100mm (4") Zirconium Sanding Flap Disc 40 grit - By far the best on the market, manufactured to the highest European Standards. Flap discs consist of a backing pad on which flaps of high quality abrasive cloth are attached. As the flaps wear down new abrasive is exposed, ensuring a constant finish throughout the long life of the disc. The exceptional lifetime of a flap disc (approx 20 times the life of a fibre disc) leads to a remarkable saving in both operator time and cost. Depressed Centre. Hole Size 16mm.