The Charge is our most durable timer and was designed to be used under the most demanding conditions. While it is the same size and offers all the functions as our , it is also weatherproof allowing for use in heavy continuous rain as well as extreme sweat and humid conditions. A backlit LCD makes it easy to see in any light exposure. It also offers the loudest beep alarm of any of our timers. Finally, the Charge has a built in rechargeable battery that will last for months on a single charge. *PLEASE NOTE - if the timer is not going to be used for an extended period of time, the battery must be charged at least once every six months.* For use with: HIIT, CrossFit, Cardio, Weightlifting, Strength Training, Kettlebells, Running, Learn-to-Run, Run-Walk-Run, MMA, Tabata, Boxing, Martial Arts and more. Compact interval timer times or intervals between seconds and 99 minutes. Built-in Stopwatch and Clock feature. Secure and Removable Belt-clip . Auto mode keeps repeating through intervals, up to 99 repeats. Chime and vibration interval notification; alarm duration can be set for , , five, or nine seconds. Backlit LCD makes it easy to see in any light exposure. Weatherproof allowing for use in heavy continuous rain as well as extreme sweat and humid conditions. Please note - Cannot be submerged in water. Do not use in a pool. Size of a small pager. Built in rechargeable battery that will last for months on a single charge. Charging cable . Fits all , including the Watchstrap.