All of our bottom bracket offerings will use an appropriate Conversion Kit specific to the brand and model of crankset to be used. Our Conversion Kits are made to account for crank manufacturers' machining tolerances and ensure they mate perfectly with our precision bearings, extending product life, and reduce the potential for noise. CONVERSION KIT #4 (PBB084) For use with ThreadFit™ 24 For cranksets with 24mm spindles. CONVERSION KIT #6 (PBB086) for SRAM GXP cranks. For use with ThreadFit™ 24, ThreadFit™ T47 24i, ThreadFit™ T47 24x 68mm, 73mm, 73mm SB , 86.5mm, 92mm, and 92mm SB BB shells. CONVERSION KIT #16 For use with ThreadFit™ 24 100mm Threaded BB Shell 24mm Mountain Cranksets Common Cranks: Shimano mountain, FSA mountain, Gravity, Race Face mountain, Surly CONVERSION KIT #17 For use with ThreadFit™ 24 100mm Threaded BB Shell 24mm to 22mm Stepped Mountain Cranksets Common Cranks: SRAM mountain, Bontrager mountain, TruVativ mountain, Zinn mountain CONVERSION KIT #20 For use with ThreadFit™ 24 68mm Threaded BB Shell 24mm BMX Cranksets Common Cranks: Shimano