Inch or metric...it works with either just as well. We've largely gone away form steel FAL/L1A1 mags as they vary so much form one to another and to their original specs, all based on where they were made, from what stampings, on what machines, and when. While the LAR-8 still works with many of them, it doesn't work with all of them. We are using a polymer magazine that is a semi hybrid of inch and metric, and because of changes that we've made ot the magwell over the years, some modification may be necessary to make it work in a particular LAR-8. A card comes with the poly mags describing two different modes that MIGHT be necessary (many rifles require no mods, some require one or the other mod, and a very few require both mods).
Short mags are few and far between right now. We stopped making the steel versions when the poly units were due, but then there were a couple of issues with the mold for the short mags, which we believe have now been resolved. We wanted them out well-ahead of fall hunting season and we missed that boat entirely.
Steve/RRA