IIRC this was a kit aiming to sell to CA residents so they could build P80s and print their own frames legally. It would attach in such a way to turn it into a strange bolt action monstrosity. I forget the specifics as it's been long enough that the details are fuzzy; absolutely do not take my word as fact here. The laws changed and it's no longer a valid way to use this product in the way the inventor intended (that I do remember!) so I guess it doesn't really matter anymore either way. I'm sure someone else will remember this better than I did.