String set-screw for a variety of Conn and King rotor valve systems on trombones and horns. This screw is used to hold the end of the string to the lever. These are used on King 606F/607F/608F, 3BF, 4BF, Conn 52H, 36H alto, old style 88H, Conn French horns including 8D, 9D, 10D and 11D, and Benge 165F.