YJ Watch Screen Protector 35 Using the latest Bluetooth 4.0 technology to ensure the most stable data transfer Ultra-low-power design, continuous working hours more than 700 hours, and standby time over 8000 hours The most advanced dynamic data collection technology to support maximum cadence 400RPM, and maximum speed 50 Mile / H Waterproof, dustproof, shockproof, and anti-theft hardware design;Compatible with all types of bicycles Support devices equipped Bluetooth 4.0 on both iOS and Android 4.3 system. ( iPhone4s, iPhone5/5c/5s )