Collum CMC Thumb Brace is designed for people with arthritis at the CMC and MCP joints of the thumb. Made of quality leather with a soft suede lining for comfort and durability. Allows performance of routine tasks in comfort because it limits extremes of motion of the joints of the thumb. Color may vary. TO determine size, with the wrist straight, measure from the bony protrusion on the thumb side of the wrist to the knuckle near the thumbnail.