Spare end pins for Grover's quick-release strap lock system, sold as a pair in nickel. Fit these to a second or third guitar and one strap with the Grover locks on it will clip onto all of them, so there's no need to buy a whole new set each time. The pins are smooth and polished so they won't chew the strap, and each comes with its mounting screw. Grover part number GP810N.