Description Features of the Corflex Boxer Splint:Anatomically designed to provide comfortable support, protection and immobilization of the 4th and 5th metacarpals.Indicated for treatment of acute or sub-acute fractures of the 4th and 5th metacarpals commonly referred to as "boxer fractures"Â.Constructed of lightweight low-density polyethylene shell with soft foam liner and palmer pad and contact closure straps.Wrist circumference: 6"-7".4th & 5th MCP joint: 3.75"-4.25".