Many thumb and wrist splints are constructed out of a rigid plastic, which can become uncomfortable against your skin over the course of the day. This black undersock adds comfort with its soft material and prevents thumb and wrist braces from rubbing or chafing against your skin. Compatible with the “BraceAbility Hard Plastic Thumb Splint | Arthritis Treatment Brace to Immobilize & Stabilize CMC, Basal and MCP Joints for Trigger Thumb, Tendonitis Pain, Sprains” sold on Amazon, fitting all 3 sizes and can be worn on your right or left hand. However, It can also be worn under most thumb and wrist splints on the market to reduce skin irritation, enhance comfort, and provide sweat protection.