Not lower quality aluminum... softer aluminum. To be honest, there is a lot of discussions about what is better for a receiver set: 6061 or 7055... We went for the 6061 because it is, in my opinion, and a lot of others is safer as it will bulge and not splinter if the firearm has a case explosion out of battery. But the receivers are hard anodized.
But yes... all other standard AR15 parts fit, except the rear retainer pin, which will come with it.
They went together without any issues or having to ream out any pin holes... the bolt catch retainer is a screw as well, not a pin, like the SAI102. ;-)
JR
Thank you