The LMB Ulnar nerve splint is for ulnar nerve injury and boxer''s fracture of the 4th and 5th metacarpal. A spring assists the flexion of the MP joints of the ring and little finger, while still allowing functional use of the hand. The flexion bar provides approximately 3.5 lbs of force. To size, measure the width of the hand at the MP joints in inches. If the measurement falls between sizes, use the larger size.