Given the long list of XX1 setup possibilities, SRAM decided to put the power directly into your hands. Now, the crank arms are being provided without a chainring, with different bottom bracket compatibilities, and in numerous Q Factors. This way, you're able to piece together your drivetrain exactly how you want it, not how you're told. So, if you're running a BB30 bottom bracket and prefer a narrower Q Factor, the SRAM XX1 BB30 Crank Arms with 156mm Q Factor are for you. Carbon fiber arms have been mated to a redesigned aluminum spider for a lightweight crank arm that doesn't require a finessing of parts in order to make an optimal single ring setup. The X SYNC chainring is designed for maximum chain control, with each tooth being CNC machined in order to support the chain's inner and outer links. This machining process provides a variable thickness from tooth to tooth, so the chain and chainring essentially lock together as you pedal. However, the locking of the two doesn't inhibit pedal efficiency, and it eliminates the commonplace ailments associated with running a single ring up front. Additionally, this system provides you with a liberation from chain guides. SRAM even went as far as to say that you have a better chance of dropping your chain with a front derailleur than you do with the XX1 crank and chain combo. The new chainring's 76 bolt circle diameter sets it apart from others in the SRAM catalog. This diameter emanated from a functionality standpoint, not as an afterthought of the new, universal spider shape. Its design makes it simple to remove the chainring for either maintenance or ratio changes. Gone are the days of finagling the chainring off of the spider just unscrew the bolts, move the chainring off, and you'll have the replacement on in minutes. Even better, SRAM has created six different chainring sizes that are compatible with the XX1 spider. Now, you're able to dial in your range to match the trail, either beforehand or on the fly....