this is why I dont buy into "a lower is a lower" BS. ill spend $20 or $30 more for a stripped lower that i know is gonna be in spec. Id be on the phone wanting a refund if the lower and the upper wouldnt fit a known in spec upper or lower they are both out of spec and i wouldnt want to roll the dice again. buy an Aero precision lower and throw a BCM or LMT upper on it.