Size Arbor Grit Maxrpm Type 4-1/2? 7/8? 36# 40# 60# 80# 120# 13300 T27 Characteristics: Provide flaps combination like Zir+Zir? Zir(no-coating) + Zir(coating)?Premium Ceramic + Ziretc, each combination can offer different performance in application. Type 27 ?flat face;nylon backing pad. Reinforce backing pad design Maximum contact with work surface without loading Cool easy and never buring working piece More durable than traditional flap disc and less downtime for disc changes increasing efficiency