Gibraltar SC-0129 6Mm Key Screw F/U-Jnt 4/Pack 6mm diameter This is a 4-pack of screws for the U-joint that adjoins your double-bass beater hub to your beater The screw is adjustable with a standard drum key This is a 4-pack of screws for the U-joint that adjoins your double-bass beater hub to your beater The screw is adjustable with a standard drum key