2 Treble, 2 bass SELF ALIGNING THRUST BEARINGS! 

Self-aligning thrust bearings! Special butterfly button. Durable cast housing. End thrust bearings. Worm meshes perfectly with gear. Safety-type string posts with cutaway shoulders to provide slip-over. Two screws in the housing apron provide greater holding power. It may be used with ALL modern bass guitar headpieces. Individually hand-tested. Screws and bushings included. 20:1 gear ratio.

For detailed specifications and/or fitting guides please locate this item on the Grover website where they offer more information.