The my zone heart rate monitor chest strap is the waterproof and sweat-proof Pro Strap, and when you're sweating profusely when training, it effectively and correctly monitors and transmits your real-time heart rate signal to your transmitter. It is an adjustable elastic replacement strap Only for Myzone MZ-switch and the new Max device;Not Compatible with MZ-3 MZ-1. 1. Specifications: A) Belt length: small, medium, or large; B) Material: nylon + spandex. C) Color: red and black 2. Features: This flexible elastic strap provides a comfortable fit. Easy to use, clean, durable, highly efficient, and stable. The soft fabrics and adaptive electrodes make it extremely sensitive to your heart's electrical signals. 3. Instruction 1) Wet the sensors on the inside of the strap. 2) Attach your heart rate monitor transmitter to the strap. 3) Attach the strap around your chest. 4) Make sure the monitor sits above the base of your chest bone. 5) Package Included: 1 x chest belt strap (only strap, not including transmitter)