Rear axle for Alexrims DC 4.5 Disc 26" MTB wheels w/ Formula hubs I've acquired a pair of old Alexrims DC 4.5 Disc 26" MTB wheels with Formula hubs, but the rear wheel is missing the axle. I've been reading various posts about how to measure / replace the axle, but haven't found anything that makes me confident enough yet to buy a replacement. Is there an easy way to tell what size / type I need? 

I initially presumed I would just need a standard axle for 5mm QR skewers, but when I measured the internal diameter of the hub it was 12mm. So is this hub actually designed for a 12mm bolt thru axle?

Any advice or pointing in the right direction would be greatly appreciated!
If the hub has a smooth, straight-walled 12mm diameter hole through it, yes it's for a 12mm through axle. (A 'through axle' isn't really the axle of course, it's a fastener that goes through the hollow axle in the hub.)

If this is the case, there are through-axle to quick release adapters available that you can use. 

BTW, have you checked that the hub width is correct for your frame?

UPDATE: Nope not through-axle. Just missing axle and bearings.