This set includes a pair of 15mm bolt on, plus 7,5,and 3mm slip on CNC aluminum gold anodized lug and hub centric spacers with 70.3 center bore 5x4.75" 120.65mm PCD & m12p1.5 ARP 100-7726 studs. The addition of $90 in ARP hardware (costing you just $60 more than our non-ARP spacers for other cars) makes these our most expensive wheel spacers yet however we take the corvette very seriously because of the high horsepower potential and high grip tires commonly found on this iconic car. We've tested these regularly in competition on our team's 1050hp Pro1 Formula Drift C6 with a 295/40/18, piloted by Matt Field. He uses these to alter the track width front versus rear, which changes side bite to forward bite ratio along with other alignment changes to customize the grip and response for each track without waiting for another set of custom width wheels to be made, which will always be better than wheel spacers however the testing for his favorite setup has to happen before the new season's wheel spec is finalized. The adjustable width with slip-on's allows great fitment with several sets of wheels despite differences in offset without buying more than one set of spacers. Drifters are always coming across new tires they want to try, but each brand has a different side wall profile. If you are like us you cant resist switching up your style by buying and selling used track wheels, without compromise in fitment.