The spline socket design offers higher strength in a more compact profile, making it common on military and commercial aircraft. Urrea spline sockets are made from high quality steel. Polished chrome plated finished. Spline size: 16. Type: I. Inches: 1/2″. MM: 13mm. Length: 5/32″. Nut end outside diameter: 1/2″. Drive end outside diameter: 7/8”. Nut depth: 9/16”.