The Garmin HRM Dual Heart Rate Monitor transmits real-time heart rate data over ANT+ connectivity and Bluetooth Low Energy technology, giving you more options to train indoors, outdoors or even online.Data-driven: Provides reliable, real-time heart rate data for maintaining or improving fitnessCompatibility: ANT+ connectivity and Bluetooth wireless technologyStrap length: Adjustable from 63.5cm to 132.0cmWater rating: 1 ATM (withstands pressures equivalent to a depth of 10 meters)Battery: User-replaceable CR2032 (3 volts)With a soft, comfortable strap, the monitor sits close to your chest and won't get in the way of your cycling or running activities. The strap is fully adjustable and washable simply remove the heart rate module. It also has an excellent battery life of up to 3.5 years with average use so you don t have to worry about it running out of juice.