Specification Brand ModelSD-520MaterialABSWaterproofYesColorBlackLength adjustment range70-120CMSize28×35×10MMBattery1x CR2032 BatteryWeight66gLanguageEnglish Features:bluetooth 4 low power transmission, use with APP to achieve data wireless transmission.Waterproof and anti sweat ...Specification Brand ModelSD-520MaterialABSWaterproofYesColorBlackLength adjustment range70-120CMSize28×35×10MMBattery1x CR2032 BatteryWeight66gLanguageEnglish Features:bluetooth 4 low power transmission, use with APP to achieve data wireless transmission.Waterproof and anti sweat, easy to clean.Equipment requirements: for Android 4.4 and above, for IOS phone with supporting bluetooth 4.0. Suitable for sports riding / cycling. Package Included: 1 x Intelligent bluetooth Heart Rate Belt