Replacement machine head with 2-screw and banjo bolt as counterfort. Schaller's new and improved Keystone tuning buttons feature vintage original specs along with that classic look and feel. Designed to match contemporary as well as historic guitar styles. Available in single-ring and double-ring versions (SR + DR). All sealed tuners are lubricated with Schaller special grease for lifetime maintenance-free service. All parts are precision-crafted and surface-finished, the self-locking drive ensures an even, delicate and steady tuning. All string posts are made of high-grade brass and fitted into the housing with utmost precision, ensuring the best possible tuning accuracy and wear resistance.