I had the 2 1/4" drive case prep bases from Herters but no bits for it. All the new stuff is 8x32 (kinda). i bought 4 Standoffs from McMaster that are 8x32 inside thread and 1/4 OD.

The tool is a chinese knockoff of a Lyman tool (was $30 cheaper than Lyman). I figured if it didn't work I'd save the money. Well it kinda works, I suspect the threads on the bits are metric.

Amazon tool.