LOL, well, umm...
Any of these new companies that seem to pop up out of nowhere. For me it's easy to share which ones I trust. They are BCM, DD, PSA, KAC, Colt, Spikes, and LMT. I am probably missing some though.
It's always good practice to find a trusted distributor like DSG Arms, PSA, BCM, Aimsurplus, and Rainier Arms. Basicly if it's for sale at any of those places it's GTG.