I found this lower receiver on rainier arms by a company called A3 Tactical. It allows the use of an AR grip, trigger and selector and also the use of Scorpion Evo mags. I installed it a few days ago and I just say that it is awesome! I had zero failures when I shot. It fits great and looks even better. If you have a bog you need this lower. A3 has a Shopify store with more stuff than what Rainer has.