3/32in Shimano splined. 9spd spaced - stack 'em up and run 'em with a mech, or singley for single speed. Assymetric for chainline tuning. Groove Armada tooth cleaning system. Oh, and we forgot to say... They've got a big wide bottom (though not as big as fat mandy that lives up the road from Shauns). We'll take a better pic sometime, but this is a good idea if fitting to a non-steel freehub body - wide based cogs spread the load and don't dig in.

Base is 4mm wide - plenty wide enough not to dig in.