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