The carbon15 is a different beast, but we've sold tens of thousands of the New Frontier Polymer Lowers with very few issues, FWIW. We've never sold a brand of lower that didn't have the occasional issue with QC, blems, etc: Including Seekins, Mega, Spike's, Aero, Anderson, etc. With that said, the rate of breakages is super low with the polymer lowers. I wouldn't want to use it for butt-stroking people, but the average guy will never push any lower to its breaking point. For a cost effective lightweight lower, they're great. If you want a "buy-once cry-once" lower then get a forged or billet lower. Most guys who own lowers have multiples for a variety of different uses.