You mean the fixing bolt that secures the crankarm to the bottom bracket?
For ISIS, it will depend on which crankset/bottom bracket you have. I find reference to M12 or M15.
Or, are you asking what size hex wrench you need to use? 8mm for the Truvativ Elita ISIS crank on my Big Buzz.
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Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Last edited by JanMM; 08-21-09 at 08:31 PM.