The part installed at the factory looks like a plain old nail, about six penny, trimmed to length. Plain as in not galvanized.

It's not a big deal to install, but the need to remove the sears to pull a fox stock makes it tedious. I would leave the sears out while you fit the length because it may take a few attempts to get it right. Maybe someone will measure one that is out of their gun to get you started. But like everything with these guns, you'll probably have to tweak the fit.