This is the miniball ball joint component of Getzen trombone valve linkages. It is used on a variety of rotary and axial flow (Thayer) valves for 1000 and 3000 series instruments. Each valve uses two ball joints, so order two if you wish to replace both.Ball joint only. Screw and nut not included. Order nuts and screws separately (items 119497 and 119498). Not interchangeable with Bach miniball parts.