The Thermoskin Elastic Back Stabilizer is anatomically designed for a more comfortable fit. Provides compression and support for general lower back dysfunctions. Built-in flexible stabilizers provide additional support to the lower back. Two adjustable side straps for extra compression. Airmesh material combines lightweight, power fabric with a breathable mesh knit for maximum ventilation and comfortable continuous wear. Sizing Guide: Measure circumference around middle of the waist. Small 25 1/2 - 29 1/2 inches. Medium 29 1/2 - 33 1/2. Large 33 1/2 - 37 1/2. X-Large 37 1/2 - 41 1/2 inches. If in doubt on Thermoskin sizing it is generally best to select the larger size.