DESC: Coded version of T31 works with all Polar monitors. Featuring new elastic design with front buckles, 25 % smaller, more stable, does not slide, increased comfort level, smaller electrode area. The Polar Transmitter is the only true 100% waterproof unit available today. No battery compartment or o-ring seal to cause leaking and failure Best choice for swimming use No exposed electronics to cause corrosion Battery life of 5-6 years based on 1 hour daily use 2 Year maintenance free warranty including the battery Compatible with all coded and non-coded Polar HRMs and Polar compatible gym equipment