I suggest consolidating your posts -
You have a post in the Technical forums basically asking the same thing, then this one in Hometown (posted an hour apart).
Helpful people are answering on both not knowing the other (same question) exists - worse, some people are not familiar with OLLs, and are suggesting you purchase a Bushmaster lower, a lower you asked about, without knowing they are banned by name in California (yes, I know the carbon lowers are legal to purchase - but it seems everyone is recommending the XM15, which is already banned).
I would suggest keeping any OLL related questions here, as many outside of California are not aware of our unique situation, and may give you advice (well meaning, of course), that may get you into legal trouble.
With all of that said, as Bill suggested, any quality forged lower will suffice. I have an affinity for CMT-made lowers. I own Stag, Noveske, and MGI lowers - all are top shelf, and the quality of the finish is exceptional (for the most part). The MGI has minor cosmetic flaws, but this is due to the additional mods required to make the lower "modular." The new MGI lowers should be billet vs the earlier forged, so you will not see these flaws on the latest from MGI.