Diameter 6″. Center hole thread size: 5/16-24 EXT. Provides excellent disc attachment yet allows quick, easy disc removal. Back up pads enable the use of 3M Stikit discs (sold separately) on a disc, random orbital, or rotary sander. Variety of densities provides flexibility for varied finishes. Dust Free (D/F) disc pads allow dust extraction capability. Variety of attachment interfaces allows use with common power tools.