Hub shells are turned out of 6xxx aluminium, axle is chromoly, and the bolts on the prototype are 3/8 NF in a grade 8... figured that for the US it would be nice to be able to find a replacement bolt at any hardware store for pennies although the custom drilled bolts are pretty sweet.

Axles can be customized with 7xxx axles and QR's, my road bike has a tommy bolt and a 15mm flat, and we can do metric bolts too.