I USE 2.2 RPM CLAWZ AND 2.2 PADDLES FITS THE 12MM HUBS, THE ONLY DOWNFALL IS THE AXLE IS JUST A BIT SHORT AND THE NUT DOES TIGHTEN BUT NOT FULLY. YOU CAN MILL THE RPM CLAWZ WHEEL CENTER WITH A DRILL BIT DOWN ABOUT 1/8 INCH AND THE NUT SHOULD TIGHTEN MORE. USE LOCKTITE IF NEEDED.