The Pcore is extremely lightweight, comfortable and effective to use. Made of revolutionary breathable mesh material, the Pcore is the most comfortable and dynamic lower back/core belt available on the market today. The Pcore now includes a removable/adjustable self heating magnetic support pad that can be used anywhere on the body for pain relief and increased circulation. Sizes (Length): When measuring size please measure around the area where you will put the belt (usually around the belly button) S: 29-34.5" (75-88cm), M: 34-37" (87-95cm), L: 36-39" (92-100cm), XL: 38-41" (97-105cm), XXL: 40-43" (102-110cm), XXXL: 42-45" (107-115cm).