This harness has been designed by Form Function to work with their STP devices. A simple vinyl panel securely holds the packer up against the genital area to ensure it stays in place during wear. The straps wrap around the thigh (where the leg meets the torso, approximately where a pair of briefs would end), and are made of an elastic material. The waist dimensions for each size are approximately the following: Small = 28-32; Medium = 32=36; Large = 36-42; XL = 42-48. Made of nylon.