Handy sanding disc that fits direct onto your lathe chuck. The dovetailed recess in the back is 55 mm. Fits most standard chucks with 100 mm diameter and jaws, including super nova, Record sc4, Vicmarc, etc. Not suitable for Axminster Clubman jaws. Disc diameter 145 mm fits 150 mm Velcro sanding pads. Just use a pair of scissors to trim the abrasive to fit the disc.