Indasa 5" Rhynofibre "Z" Silver Resin Fiber Grinding Discs (1200 Series) are a premium abrasive featuring zirconium mineral grain, durable vulcanized backing, high strength resin to eliminate shredding and high initial cutting action. Excellent quality - offers high initial cut, better heat resistance, better edge stability and last far longer than low quality discs flooding the market. Zirconium abrasive grain is perfect for machine grinding and sanding of metal work as it stays cooler and sharper than aluminum oxide. Sold 25 discs per box. Also available in 7" size with 7/8" hole.