Just received my new Full Frame Module from Sig for my 320 and in the box it also had a package with an extra slide catch lever in it, does anybody know why?

The company does not know which grip frame you have. One lever fits original frames, one lever fits newer frames AND original frames. But, some people prefer the original bigger lever with the original grip.

Yep. I hate the bigger one, that and it’s rearward orientation makes me ride it while shooting.