Fibre sanding disc is made of synthetic resin and abrasive materials coated on fibre backing disc.It is uesed for machine,ship building, aviation, bridge, construction, etc... Backing Bonds Materials Grit Size Fibre paper Resin /Glue A /C/ZA... P16#--P240# 4"(100mm) x 16mm 4.5"(115mm)x16(22)mm 5"(125mm) x 22mm 6"(150mm) x 22mm 7"(180mm) x 22mm 9"(230mm) x 22mm Sanding disc with valcro backing is made of flannel cloth adhere to the back of abrasive paper or abrasive cloth.It can be punched to circular, triangle,or other special shapes.It is pasted up hard rubber disc pneumatic or electric tool.It is mainly used for polishing auto surface, wood , stone material, metal, etc... The waste scraps can go out from the holes,so the workpiece can not be harmed and there is no evironment pollusion.