The Incredible Calf Master Stretch/Flexibility Training System. Includes a 3 minute download of Stacey's recommended exercises. By deep stretching the Achilles tendon, it enables the stretch to go all the way up the hamstrings to clear tightness behind the knee and improve extension which increases flexibility, sports performance and range of motion. Every beginner, dancer, martial artist, gymnast, figure skater, athlete or anyone with tight calf, knee, hamstring and Achilles pain would benefit by making this a part of your training routine.