We also have 6-rib pulleys for 20mm or 0.785" shafts: Click Here
6-rib Pulleys Available for 17mm shafts:
TOP QUALITY! Our supercharger pulleys are made from a single 6064 alloy aluminum billet, and turned to an accuracy within .001 of an inch. Unlike poorly-made pulleys that have straight-cut belt vees - that cause belt slippage - ours are properly V-Cut for maximum belt contact! Then, the Red and Blue pulleys are sent off to be anodized for toughness and good looks. Natural-finish (silver) pulleys are not anodized.
DIAL IN YOUR BOOST! Measure your current supercharger pulley across the belt lands as shown in the photo below. The next smaller size pulley will create more boost than you have now. Racers also exchange pulleys to bring the boost in right where they want it to match their gearing.
A GENERAL RULE of THUMB: on a properly tuned and fueled engine, you should gain about 20 HP per 1 PSI of boost.
Pulley Sizing Advice: What is the right-size pulley for your Powerdyne application? Click Here