The Sacroiliac joint and the Pelvis are the foundation of your spine, (where a lot of weight is carried), and for many, it's the source of that dull ache. The Back Pain Belt can help by applying firm, but gentle support to your lower back. By adding support to this area, your back muscles can relax, blood flow can increase, and your pain can be eliminated or reduced. The Back Pain Belt is light and allows you to adjust the amount of tension you desire. Regular 4" x 40", Large 4" x 51", XL 4" x 62".