Features and Benefits: 3M™ 990 Mandrel Designed for use with the 3" x 3/8" radial bristle discs (PNs 07542, 07543, 07544) Allows stacking of one to four discs depending on the width of the surface to be cleaned 1-3/4" x 1/4" mandrel shank size and 3/8" center hole....(more info)