3M 5621 Disc Retainer Nut, 1/2in 11 Int, PK10. More details: Disc Retainer Nut, Dia 1/2 In, For Use With For use with all 3M(TM) disc pad hub and face plates, non 3M fibre disc holders. Has a 5/8-11 INT thread and has 5/8 In thread length. Has 1/4 In diameter holes for use with a spanner wrench., Package 10