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. Construction: Closed Button: Keystone single ring Gear ratio: 1:16 Shaft length: 21.7 mm Bore: 9.8 mm