The Schaller Buttons for S-Locks are available as spares so you can use one strap equipped with Schaller strap locks across multiple guitars with S-Lock buttons installed. The strap button and screw are made from one piece of solid hardened steel for extra strength over the old separate screw and strap button design. The strong 4 mm self-tapping wood screw keeps your guitar safe when playing with a strap and tightens with a 3 mm allen/hex wrench. Set of two buttons come with felt washers to protect the guitars finish.