The Brembos fitted to the Hayabusa are M4s correct?I googled the part number in my picture (220A02421) and it looks like it is 10 mm. Revzilla sells them so they may be able to tell you exactly. Not the GP4 spacers are type C. Don't know what that means exactly but you should check as these are pretty specific fit parts.
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Are the spacers required gauges off of the fork type or caliper type generally?