Smart Fitness Trackers
Found 563 items
- Specifications
- Brand: Apple
- Model: MWXF3LW/A
- product_dimensions: 24 x 7.7 x 3 inches
- item_weight: 4.8 ounces
- department: mens
- manufacturer: Apple
- country_of_origin: China
- batteries: 1 Lithium Ion batteries required. (included)
- date_first_available: September 9, 2024
- Specifications
- Brand: Samsung
- Model: SM-R950NZKAXAA
- Product Dimensions: 1.67 x 0.43 x 1.67 inches
- Item Weight: 7.4 ounces
- Batteries: 1 Lithium Ion batteries required. (included)
- OS: Android
- Wireless Communication Technologies: Bluetooth
- Connectivity Technologies: Bluetooth, Wi-Fi
- GPS: True
- Special Features: Durable
- Other Display Features: Wireless
- Human Interface Input: Touchscreen
- Scanner Resolution: 390 x 390
- Whats in the Box: Watch Strap, Galaxy Watch Charger, Watch Body
- Manufacturer: SAMSUNG
- Country of Origin: Vietnam
- Date First Available: July 26, 2023
- Weight: 0.21 Kilograms
- Standing Screen Display Size: 43 Millimeters
- Memory Storage Capacity: 16000 MB
Activity Tracker Accessories
Samsung SM-R940NZKDAMZ Custom style with unique watch faces
$566.99
$279.00
- Specifications
- Brand: Samsung
- Model: SM-R940NZKDAMZ
- package_dimensions: 11.02 x 2.36 x 1.46 inches
- item_weight: 7 ounces
- batteries: 1 Lithium Ion batteries required. (included)
- os: Android
- connectivity_technologies: Bluetooth, Wi-Fi
- gps: Built-in GPS
- special_features: Heart Rate Monitor
- other_display_features: Wireless
- human_interface_input: Touchscreen
- whats_in_the_box: Watch Strap, Galaxy Watch Charger, Watch Body
- standing_screen_display_size: 44 Millimeters
- Specifications
- Brand: WHOOP
- Model: 973-002-000
- material: Nylon
- compatible_devices: Smartphones, Tablets
- item_weight: 4 ounces
- battery_life: 14 days
- product_dimensions: 7.36 x 2.65 x 1.34 inches
- batteries: 1 Lithium Metal batteries required. (included)
- country_of_origin: China
- Specifications
- Brand: Ultrahuman
- Model: RA-RT-Size14-US
- package_dimensions: 8.7 x 6.69 x 3.31 inches
- item_weight: 2.86 Grams
- batteries: 1 Lithium Polymer batteries required. (included)
- memory_storage_capacity: 0.5 MB
- country_of_origin: India
- date_first_available: July 11, 2024
- Specifications
- Brand: Oura
- Model: JZ90-54217-10
- product_dimensions: 1.06 x 1.06 x 0.28 inches
- item_weight: 6.3 ounces
- batteries: 1 Lithium Polymer batteries required. (included)
- connectivity_technologies: Bluetooth
- special_features: Heart Rate Monitor, Activity Tracker
- whats_in_the_box: Oura Ring 4, Oura Ring 4 Charger, USB Cable, Information Booklet, Quick Start Guide
- manufacturer: Oura
- country_of_origin: Estonia
- date_first_available: October 3, 2024
- ram_memory_installed_size: 16 MB
- Specifications
- Brand: Oura
- Model: JZ90-54217-09
- product_dimensions: 1.02 x 1.02 x 0.28 inches
- item_weight: 6.3 ounces
- batteries: 1 Lithium Polymer batteries required. (included)
- connectivity_technologies: Bluetooth
- special_features: Heart Rate Monitor, Activity Tracker
- human_interface_input: Buttons
- whats_in_the_box: Oura Ring 4, Oura Ring 4 Charger, USB Cable, Information Booklet, Quick Start Guide
- manufacturer: Oura
- country_of_origin: Estonia
- date_first_available: October 3, 2024
- ram_memory_installed_size: 512 KB
- Specifications
- Brand: aabo
- Model: ABRING7S
- Product Dimensions: 2.72 x 4.17 x 4.17 inches
- Item Weight: 7.4 ounces
- Batteries: 1 Lithium Ion batteries required.
- Date First Available: March 13, 2024
- Specifications
- Brand: Apple
- Model: MR9C3LW/A
- Product Dimensions: 9.53 x 3.07 x 1.3 inches
- Item Weight: 8.1 ounces
- Department: mens
- Manufacturer: Apple
- Country of Origin: Vietnam
- Batteries: 1 Lithium Ion batteries required. (included)
- Date First Available: February 1, 2024
Wrist & Arm Wearables
RENPHO Smart Ring Comprehensive health and fitness tracking
$229.00
$219.00
- Specifications
- Brand: RENPHO
- Model: Smart Ring
- Battery Life: 7 days
- Waterproof: 5ATM
- Material: Titanium
- Compatibility: iOS, Android, Apple Health, Google Health Connect
- Health Tracking: Sleep, Blood Oxygen Levels, Stress, Heart Rate, Steps, Distance, Calories Burned
- Specifications
- Brand: RENPHO
- Model: LYNX
- Product Dimensions: 0.78 x 0.78 x 0.12 inches
- Item Weight: 0.17 Ounces
- Batteries: 1 Lithium Ion batteries required. (included)
- Date First Available: February 26, 2025
- Specifications
- Brand: Csasan
- Model: T70
- Product Dimensions: 3.72 x 0.79 x 6.89 inches
- Item Weight: 3.52 ounces
- Batteries: 1 Lithium Polymer batteries required. (included)
- Standing Screen Display Size: 1.91 Inches
- Country of Origin: China
- Specifications
- Brand: Oura
- Model: JZ90-1003-08
- Product Dimensions: 0.91 x 0.91 x 0.28 inches
- Item Weight: 8 ounces
- Batteries: 1 Lithium Ion batteries required. (included)
- Customer Reviews: 3260 ratings, 4.3 stars
- Other Display Features: Wireless
- What's in the Box: Oura Ring, Charger, USB Cable, Information Booklet, Quick Start Guide
- Department: unisex-adult
- Manufacturer: Oura
- Country of Origin: Estonia
- Date First Available: January 19, 2024
- Specifications
- Brand: Fitbit
- Model: Versa 4
- Product Dimensions: 1.57 x 0.43 x 1.57 inches
- Item Weight: 6.3 ounces
- Batteries: 1 Lithium Ion batteries required.
- Wireless Communication Technologies: Bluetooth
- GPS: Built-in GPS
- Special Features: Activity Tracker, GPS, Heart Rate Monitor, Sleep Monitor, Daily Workout Memory, Water Resistant, Alarm Clock, Bluetooth, Text Messaging, Phone Call
- Color: Black/Graphite
- What's in the Box: Fitbit Versa 4 Fitness Smartwatch, S & L Bands, Charger
- Standing Screen Display Size: 1.58 Inches
- Memory Storage Capacity: 4 GB
- Specifications
- Brand: Amazfit
- Model: W2321TY1N
- Product Dimensions: 1.01 x 1.01 x 0.31 inches
- Item Weight: 4 Grams
- Batteries: 1 Lithium Polymer batteries required. (included)
- Date First Available: July 16, 2024
- Country of Origin: China
- Specifications
- Brand: Anarow
- Model: SmartHealth
- Compatibility: Android 5.1, iOS 8.0 and above
- Waterproof Rating: 5ATM
- Battery Life: 3-5 days normal use, 7-10 days standby
- Charging Time: 60 minutes
- Material: Lightweight aluminum alloy
- Specifications
- Brand: Oulencu
- Model: Smart Ring Health Tracker
- Item Weight: 0.1 Ounces
- Warranty Description: 1 year manufacturer
- Material: Resin, Metal
- Number of Items: 1
- Manufacturer: OULENCU
- Included Components: OULENCU Smart ring, Chargingh Cable, Quick Guide Leaflet
- Date First Available: March 10, 2025
- Specifications
- Brand: JIANVNUI
- Model: JIANVNUI
- package_dimensions: 3.54 x 3.15 x 1.42 inches
- item_weight: 3.52 ounces
- batteries: 1 9V batteries required.
- customer_reviews: ratings_count: 10, stars: 4.1
- date_first_available: March 18, 2025
- country_of_origin: China
- standing_screen_display_size: 1 Picometer
- memory_storage_capacity: 1.5 MB
- Specifications
- Brand: Kimeag
- Model: H31
- Package Dimensions: 11.42 x 3.54 x 0.75 inches
- Item Weight: 5 ounces
- Batteries: 1 Lithium Polymer batteries required. (included)
- OS: Android and ios
- Wireless Communication Technologies: Bluetooth
- GPS: GPS Via Smartphone
- Human Interface Input: Touchscreen, Dial
- Whats in the Box: Two watch bands
- Standing Screen Display Size: 1.91 Inches
Wrist & Arm Wearables
Shenzhen Buzz Tech CO.,LTD P110 Heart rate and blood oxygen monitor
$69.99
- Specifications
- Brand: Shenzhen Buzz Tech CO.,LTD
- Model: P110
- Display: 2.06 Inches, AMOLED, Touchscreen
- Connectivity: Bluetooth
- Waterproof: IP68
- Battery: Lithium Polymer, Included
- Special Features: Fitness Tracker, Phone Call, Sleep Monitor, Blood Oxygen Monitor, Heart Rate Monitor, Calorie Tracker, Alarm Clock, Stopwatch, Timer, Pedometer, Camera Control, Music Playback/Control, Sedentary Reminder, Weather, Notifications
- Compatibility: Android, iPhone, Samsung
- Specifications
- Brand: KNGAD
- package_dimensions: 3.6 x 3.55 x 1.2 inches
- item_weight: 3.2 ounces
- batteries: 1 A batteries required. (included)
- date_first_available: April 17, 2025
- country_of_origin: China
- Specifications
- Brand: Duobuy
- package_dimensions: 3 x 3 x 2 inches
- item_weight: 3.98 ounces
- batteries: 1 A batteries required. (included)
- customer_reviews: ratings_count: 23, stars: 4.4
- date_first_available: December 13, 2024
- manufacturer: Duobuy
- country_of_origin: China
- Specifications
- Brand: Emerhome
- Model: R11
- package_dimensions: 3.98 x 3.11 x 1.26 inches
- item_weight: 0.004 ounces
- batteries: 1 9V batteries required. (included)
- os: Android Wear 2.9
- connectivity_technologies: Bluetooth
- gps: No GPS
- special_features: Gesture Control, Lightweight, Multisport Tracker, Activity Tracker, Wireless Charging
- other_display_features: Wireless
- battery_power_rating: 1 Amp Hours
- whats_in_the_box: User Manual, smart ring
- country_of_origin: China
- date_first_available: March 20, 2025
- weight: 0.1 Grams
- standing_screen_display_size: 1 Inches
- memory_storage_capacity: 100 MB
- Specifications
- Brand: abcc
- Model: R11m
- package_dimensions: 2 x 2 x 2 inches
- item_weight: 0.64 ounces
- date_first_available: January 2, 2025
- country_of_origin: China
- standing_screen_display_size: 7
- memory_storage_capacity: 64 MB
- Specifications
- Brand: VNEXFU
- item_package_dimensions: 3.4 x 3.4 x 1.3 inches
- package_weight: 0.05 Kilograms
- included_components: Smart Ring*1, Charging Case*1, USB Charging Cable*1, User Manual*1
- size: #7
- customer_reviews: 4.9 stars, 29 ratings
- date_first_available: March 16, 2025
Activity Tracker Accessories
Smart Ring Health Tracker Ultra-thin and comfortable design
$57.99
$61.10
- Specifications
- Brand: Uni-Green
- Package Dimensions: 3.03 x 2.99 x 2.05 inches
- Item Weight: 2.39 ounces
- Batteries: 1 Nonstandard Battery batteries required. (included)
- Memory Storage Capacity: 0.07 MB
- Country of Origin: China
- Specifications
- Brand: Delcast
- package_dimensions: 3.58 x 3.5 x 1.85 inches
- item_weight: 4.2 ounces
- batteries: 1 AA batteries required
- standing_screen_display_size: 10
- Specifications
- Brand: Gwenland
- Model: SR08
- Package Dimensions: 7.4 x 2.95 x 1.26 inches
- Item Weight: 5.6 ounces
- Batteries: 1 AAA batteries required. (included)
- Standing Screen Display Size: 0.2 Inches
- Country of Origin: China
- Date First Available: December 31, 2024
- Specifications
- Brand: GADIXY
- Display: 1.47 Inches
- Battery Life: 5 days heavy use, 8-10 days daily use, 20 days standby
- Waterproof: IP68
- Compatibility: iOS 8.0 and above, Android 4.4 and above
- Connectivity: Bluetooth
- Memory: 260 MB
Activity Tracker Accessories
Smart Ring Health Tracker with Display Screen & Touch Button
$49.98
$59.99
- Specifications
- Model: 2025
- Display: LED display screen
- Features: Heart rate monitoring, Blood oxygen monitoring, Sleep tracking, Step counting, Multiple sports modes
- Waterproof: IP68
- Weight: 3.5g
- Compatibility: Bluetooth connection
Wrist & Arm Wearables
Smart Ring Health Tracker with Display Screen & Touch Button
$49.98
$59.99
- Specifications
- Model: 2025
- Display: LED display screen, Touch button
- Health Metrics: Heart rate, Blood oxygen, Sleep duration, Step count
- Sports Modes: Walking, Running, Hiking, Cycling, Golf
- Waterproof: IP68
- Weight: 3.5g
Wrist & Arm Wearables
Dongguan Jiajin Electronic Technology Co., Ltd SR08 All-Day Health Monitor
$47.99
$58.99
- Specifications
- Brand: Dongguan Jiajin Electronic Technology Co., Ltd
- Model: SR08
- Package Dimensions: 3.15 x 3.15 x 1.07 inches
- Item Weight: 3.39 ounces
- Batteries: 1 Lithium Ion batteries required. (included)
- Country of Origin: China
- Specifications
- Brand: Hivisuals
- Model: R18
- package_dimensions: 3.15 x 3.15 x 1 inches
- item_weight: 0.1 Kilograms
- batteries: 1 AA batteries required. (included)
- standing_screen_display_size: 1 Centimeters
- memory_storage_capacity: 10 MB
- waterproof: IP68
- Specifications
- Brand: Huawei
- Model: HUAWEI Band 8
- package_dimensions: 4.81 x 3.63 x 1.56 inches
- item_weight: 3.98 ounces
- batteries: 1 Nonstandard Battery batteries required. (included)
- standing_screen_display_size: 1.47 Inches
- memory_storage_capacity: 512 MB
- country_of_origin: China
- Specifications
- Brand: Oucscru
- Package Dimensions: 3.5 x 3.5 x 2.7 inches
- Item Weight: 0.8 Ounces
- Batteries: 1 Nonstandard Battery batteries required. (included)
- Memory Storage Capacity: 8 MB
- Country of Origin: China
- Specifications
- Brand: Coucur
- Model: Y66
- Display Size: 1.96 Inches
- Memory Storage Capacity: 1000 MB
- Waterproof Rating: IP68
- Battery Life: Up to 7 days
- Compatibility: Android, iOS
- Specifications
- Brand: Qjijolz
- Model: R5
- package_dimensions: 3.54 x 3.54 x 1.81 inches
- item_weight: 5 ounces
- batteries: 1 AAA batteries required. (included)
- memory_storage_capacity: 500 MB
- country_of_origin: China
Wrist & Arm Wearables
Shenzhen Yawell Intelligent Technology Co.,Ltd 315c59d3-cbd2-4039-8405-7f4703420088
$39.99
$40.99
- Specifications
- Brand: Shenzhen Yawell Intelligent Technology Co.,Ltd
- Model: 315c59d3-cbd2-4039-8405-7f4703420088
- package_dimensions: 4.06 x 3.11 x 1.26 inches
- item_weight: 2.39 ounces
- batteries: 1 Lithium Polymer batteries required. (included)
- standing_screen_display_size: 0.8 Centimeters
- country_of_origin: China
- Specifications
- Brand: Oucscru
- package_dimensions: 3.5 x 3.5 x 2.7 inches
- item_weight: 0.8 Ounces
- batteries: 1 Nonstandard Battery batteries required. (included)
- memory_storage_capacity: 4 MB
- country_of_origin: China
- Specifications
- Brand: FOSMET
- Model: DG10
- Package Dimensions: 6.3 x 3.66 x 1.26 inches
- Item Weight: 8.4 ounces
- Batteries: 1 A batteries required. (included)
- Standing Screen Display Size: 1.57 Inches
- Country of Origin: China
- Specifications
- Brand: GYSOA
- Model: R11M
- Package Dimensions: 4 x 3.75 x 1.25 inches
- Item Weight: 3.98 ounces
- Batteries: 1 9V batteries required. (included)
- Customer Reviews: 5 stars (19 ratings)
- Date First Available: March 10, 2025
- Country of Origin: China
- Waterproof Rating: IP68
- Battery Life: 3-5 days
- Specifications
- Brand: viohead
- Model: Smart ring
- Package Dimensions: 1 x 1 x 1 inches
- Item Weight: 0.16 ounces
- Standing Screen Display Size: 1 Inches
- Date First Available: November 1, 2024
- Specifications
- Brand: UniJethro
- Model: SR11M
- Product Dimensions: 2 x 0.31 x 2 inches
- Item Weight: 4.6 ounces
- Batteries: 1 Lithium Polymer batteries required. (included)
- OS: IOS & Android
- Connectivity Technologies: Bluetooth
- Special Features: Remote Photography, Family Care, Blood Pressure Monitor, Fitness and Activity Tracker, Blood Oxygen Monitor, Emotional Stress Monitor, Heart Rate Monitor, Sleep Tracker
- What's in the Box: Smart Ring, Charging Case, Ring Protector
- Memory Storage Capacity: 4 MB
- Specifications
- Brand: Oritham
- Model: G208
- package_dimensions: 8.31 x 3.62 x 0.75 inches
- item_weight: 4.6 ounces
- batteries: 1 9V batteries required. (included)
- standing_screen_display_size: 1.19 Inches
- memory_storage_capacity: 64 MB
- country_of_origin: China
- date_first_available: April 7, 2025
- Specifications
- Brand: YULUCKGO
- Model: SRC10
- Dimensions: 3.94 x 3.66 x 1.34 inches
- Weight: 0.09 Kilograms
- Warranty: 1 Year Manufacturer
- Included Components: Charging Cable
- Size: 9#(18.9mm)
- Sport Type: Multi-Sports
- Specifications
- Brand: SHEN ZHEN HAO CHENG TECHNOLOGY CO.,LTD
- Model: S10
- package_dimensions: 10.94 x 3.5 x 0.87 inches
- item_weight: 5.3 ounces
- batteries: 1 Lithium Polymer batteries required. (included)
- standing_screen_display_size: 1.39 Inches
- memory_storage_capacity: 1 GB
- Specifications
- Brand: RUIMEN
- Model: H1
- product_dimensions: 9.96 x 1.54 x 0.43 inches
- item_weight: 56.6 Grams
- batteries: 1 Lithium Polymer batteries required. (included)
- standing_screen_display_size: 1.85 Inches
- memory_storage_capacity: 128 MB
- Specifications
- Brand: GRV
- Model: FC1
- Product Dimensions: 9.84 x 1.38 x 0.67 inches
- Item Weight: 1.2 ounces
- Batteries: 1 Lithium Metal batteries required. (included)
- OS: iOS Phones like iPhone 11/12/13/14 series, iPhone X/XR/XS/XS Max, iPhone 8/7/6/5/4 series, iPhone SE, Android Phones like Samsung, SONY, HTC, LG, Motorola, Huawei, Xiaomi, Lenovo and other phones with Android 4.4 and above and iOS 8.0 and above
- Connectivity Technologies: Wireless
- Special Features: Activity Tracker
- Human Interface Input: Touchscreen
- Scanner Resolution: 176 x 176
- Whats in the Box: Charging cable, user manual
- Standing Screen Display Size: 1.83 Inches
- Memory Storage Capacity: 128 MB
- Specifications
- Brand: UXOXU
- Model: UXOXU-01
- Product Dimensions: 11.3 x 4.3 x 4.7 inches
- Item Weight: 3.52 ounces
- Batteries: 1 CR5 batteries required. (included)
- Date First Available: December 11, 2024
- Manufacturer: UXOXU
- Country of Origin: China
- Memory Storage Capacity: 4 MB
Wrist & Arm Wearables
SHANG WING Fitness Tracker 2025 Ver. Answer/make calls with built-in speaker
$26.99
$39.99
- Specifications
- Brand: SHANG WING
- Model: Fitness Tracker 2025 Ver.
- package_dimensions: 10.59 x 3.39 x 0.75 inches
- item_weight: 38 Grams
- batteries: 1 9V batteries required. (included)
- standing_screen_display_size: 1.85 Inches
- Specifications
- Brand: Jawploy
- Model: PX02
- Package Dimensions: 3.54 x 3.23 x 1.14 inches
- Item Weight: 3.17 ounces
- Batteries: 1 CR5 batteries required.
- Customer Reviews: 4.7 stars from 67 ratings
- Date First Available: January 8, 2025
- RAM Memory Installed Size: 96 KB
- Waterproof: 5ATM
- Material Process: Titanium alloy tenpouring glue technology
- Weight: 4.5g
- Operating Temperature Range: 0-50℃
- Charging Time: Two hours for case, 30min for ring
- Standby Time: 10-15 days(30+days when used in conjunction with charging case)
- Normal Using Time: 7-9 days
- Specifications
- Brand: Jugeman
- Model: P99
- package_dimensions: 6.42 x 3.74 x 0.67 inches
- item_weight: 3.2 ounces
- batteries: 1 A batteries required. (included)
- standing_screen_display_size: 1.96 Inches
- memory_storage_capacity: 1 GB
- country_of_origin: China
- Specifications
- Brand: Cillso
- Model: S10
- Display Size: 1.39 Inches
- Waterproof Rating: IP68
- Battery Life: Up to 30 days standby
- Compatibility: iOS 9.0+, Android 5.0+
- Sports Modes: 110+
- Watch Faces: 200+
- Package Dimensions: 10.87 x 3.58 x 0.79 inches
- Item Weight: 3.84 ounces
Wrist & Arm Wearables
Smart Watch for Women Fitness Tracker Advanced Health & Life Management
$20.99
$19.99
- Specifications
- Brand: GADIXY
- package_dimensions: 6.26 x 3.54 x 1.06 inches
- item_weight: 3.52 ounces
- batteries: 1 AAA batteries required.
- os: iOS 8.0 and above, Android 4.4 and above
- connectivity_technologies: Bluetooth
- gps: GPS Via Smartphone
- special_features: Fitness Tracker, Sleep Monitor, Blood Oxygen (SpO2), Heart Rate Monitor, Calorie Tracker, Clock, Stopwatch, Timer, Pedometer, Camera Control, Music Player, 200 Watch Faces, 25 Sports, Real-time Weather, Message & Call Notification
- other_display_features: Wireless
- human_interface_input: Touchscreen
- whats_in_the_box: User Manual, Pink silicone band, Charging Cable, Brown woven watch band
- manufacturer: GADIXY
- country_of_origin: China
- date_first_available: February 28, 2025
- standing_screen_display_size: 1.47 Inches
- memory_storage_capacity: 260 MB
- Specifications
- Brand: Soudorv
- Model: T70
- package_dimensions: 6.89 x 3.74 x 0.79 inches
- item_weight: 3.2 ounces
- batteries: 1 A batteries required. (included)
- standing_screen_display_size: 1.91 Inches
- Specifications
- Brand: Jugeman
- Model: P99
- Display: 1.96 Inches, HD Touch Screen
- Memory: 1 GB
- Waterproof: IP68
- Battery: 1 A batteries required. (included)
- Compatibility: iOS 10.0 and above, Android 9.0 and above
- Specifications
- Material: Medical-grade titanium
- Connectivity: Bluetooth 5.0
- Waterproof Rating: IP68
- Battery Life: Up to 5 days
- Compatibility: iOS, Android
- Specifications
- Brand: TRAUSI
- Model: TG08
- package_dimensions: 5.67 x 3.23 x 0.67 inches
- item_weight: 1 Grams
- batteries: 1 A batteries required. (included)
- standing_screen_display_size: 1.83 Inches
- Specifications
- Brand: BandSmith
- Model: Celular
- package_dimensions: 2.44 x 2.44 x 0.67 inches
- item_weight: 0.317 ounces
- country_of_origin: China
- date_first_available: March 24, 2024
Wrist & Arm Wearables
Health Tracker Smart Ring Real-time Health Tracking Smart Ring
$0.00
$39.99
- Specifications
- Brand: Oucscru
- package_dimensions: 3.5 x 3.5 x 2.7 inches
- item_weight: 0.8 Ounces
- batteries: 1 Nonstandard Battery batteries required. (included)
- memory_storage_capacity: 4 MB