They seem to work most with Spyderco, Benchmade, DPx, ZT, Boker and Lionsteel.
They say they take inquiries on any sort of knife, because they do have a lot of knives in their personal library, so check 'em out. There are limits, though --they do have some Fox knives and apparently even some Real Steels, but I was hoping to pick up some custom grips for a couple of Fox 479s, and my Real Steel Thor, and those were all a no go. And they don't have any Two Suns yet. (Which is a good thing honestly because I coulda got in trouble there.)