way to go, with a Model One Sales upper and "guts". The result is a low cost AR that works fine. KT's lowers have the buttstock hole already threaded, and both sides of the lower are "dimpled" where you have to drill the other holes. They are well worth the (double) cost of the Tannery Shop and other lowers. The buttstock hole is not CENTERED, nor is it STRAIGHT in the castings, so you have to make a holding jig for the lathe, use an indicator and 4 jaw chuck to bore that hole, and then thread it, or you risk having your stock on the lower crookedly. Then your buffer and spring will bind in the stock, and you CAN'T get away with "tweaking' cast aluminum, in order to straighten out the situation. Such a lower is just ruined, that's all.