4-in-line SELF ALIGNING THRUST BEARINGS! Gear ratio is 20:1. Special butterfly button. Durable cast housing. End thrust bearings. Worm meshes perfectly with gear. Safety-type string with cutaway shoulders to provide slip-over. Two screws in housing apron provide greater holding power. May be used with ALL modern bass guitar headpieces. Individually hand tested. Screws and bushings included.