Detailed Product Description Fiberglass backing pad for flap discType :T27/29 Layers:4-13 Metal Ring: 1 or 2. Outer diameter: 75mm, 85mm, 95mm, 107mm. 117mm, 140mm, 170mm 180mm It is adopted of Multi-Layer stack of compression molding in the mold after curing by heating.It is the base material of flap discs with the features of light weight,high strength and good adhesive properties etc.