The ZPE MKII hub is designed to allow for the smallest pulleys possible on factory GM vehicles. With a OD of 1.86″ pulley sizes under 2.15 are possible. We machine our hubs to be within +_ 0.00015 on the hubs bore. This allows for repeatable performance on the press for every kit. The MKII hub has a 10 bolt pattern using a M5x.08 found in no other 10 bolt hub. If our super compact hub, upgraded M5 bolts, and precision machining west not enough we also offer our M5 bolts in custom Titanium 6AL-4V T30 Torx shoulder socket caps.