Constructed of neoprene rubber using an aluminum hub with 5/8" smooth bore; no threads, fits more toolsDesign allows air to flow through the slotted hub and between the spirals on the face of the pad, keeping the disc coolHelps extend the life of the coated abrasive discIdeal for all sanding operations on metal, plastic fiberglass, etcEach pad is made individually in a single mold, then tested for perfection