Selden makes 50/50 fiberglass/polyamide composite mast swivels to enable you to trim your cunninghams, spinnakers, and vangs better. These swivels can be fitted right-side up or upside down depending on the desired orientation and function of the cam cleat. The ball bearing sheave can be above or below the swivel. The Mast Swivel/Cam Cleat 27 is designed for 9/32 in. (7mm) maximum diameter line.