Descriptions The M3 X-Strap is primarily used for TORSO SIDE CRUNCH & SIDE TWIST and GIANT CRUNCH. The TORSO SIDE CRUNCH & SIDE TWISTS are among the top 5 best exercises in the world to strengthen, tighten, and tone the obliques and waist muscles. If you dont want a smaller and tighter waist, do not get the M3 X-strap. ;)Only compatible with M3 models, including: M3, M3S, M3K, M3X, EVOWe are an Authorized Retailer for Lagree Fitness.