THE FLEX ARMS Accessory Pack - Bicep and Tricep Muscle Toner (requires THE FLEX BELT Controller - sold seperately) Improve maximum muscle strength of the biceps and triceps and save time while exercising both arms at once High Performance Muscle Training System - clinically demontrated EMS technology Convenient and easy-to-use with custom programs for beginners to fitness enthusiasts with 3 Training Programs and 99 Levels FDA cleared to tone, firm & strengthen the major upper arm muscles with results you can see and feel Requires the FLEX BELT CONTROLLER (sold separately).