SRAM Disc Brake Mount Adapters for mounting disc brake calipers onto a bike frame or fork. These adapters enable the use of 160mm, 180mm, 203mm or 220mm rotors on most Postmount frame/fork combinations. ________ Forks & Frames with 140mm Post mount: 160mm rotor use: 20 P (Front 180mm/Rear 160mm) 00.5318.007.005 180mm rotor use: 40 P (Front 200mm/Rear 180mm) 00.5318.007.006 Forks & Frames with 160mm Post mount: 160mm rotor use: NO ADAPTER 180mm rotor use: 20 P (Front 180mm/Rear 160mm) 00.5318.007.005 200mm rotor use: 40 P (Front 200mm/Rear 180mm) 00.5318.007.006 Forks & Frames with 180mm Post mount: 180mm rotor use: NO ADAPTER 200mm rotor use: 20 P (Front 180mm/Rear 160mm) 00.5318.007.005 220mm rotor use: 40 P (Front 200mm/Rear 180mm) 00.5318.007.006 Frames with 203mm Post mount: 203mm rotor use: NO ADAPTER 220mm rotor use: 17 P (Rear 220mm) 00.5318.007.008NOTE: DO NOT use for front, not compatible with 203mm fork pots mount