Looks like a good deal. (I don't know) Thought I'd pass this along.
http://shop.si-defense.com/SI_Defense_AR_15_7075_Forged_Lower_Receiver_p/si ar-15 lwr-frg.htm
http://shop.si-defense.com/SI_Defense_AR_15_7075_Forged_Lower_Receiver_p/si ar-15 lwr-frg.htm