The Kluson Contemporary Series 19:1 ratio locking tuning machine uses the more desireable rear knob locking system and is designed for usage on contemporary guitars. This design requires an individual mounting hole location offset at approximately 7 O'clock or 4 O'clock depending on left or right handed application (bass or treble side). Uses the common modern in. (10mm) peghole with a hex head type screw-in bushing and single mounting screw. This is a 6 in line set of tuning machines for right handed instruments (non-reverse headstocks) with all mounting hardware included