Polar G1 GPS Speed and Distance Sensor GPS sensor for calculating speed and distance during low-speed sports Compatible with Polar RS200, RS400, S625X, and S725X training computers Ideal for running, kayaking, cross-country skiing, and inline skating Battery life of up to 10 hours (regular mode) or 15 hours (low-power mode) Speed range of 0 to 18.3 miles per hour; weighs only 2.82 ounces