I had a 180b with a polymer lower around 2010ish and despite all the opinions of people saying it would only break if you abused the rifle I had a different experience. I knew the hinge was a weak point and went to great lengths to protect it, including laying it down on a table and carefully breaking it open to clean it. Despite my precautions after a full day at the range and several hundred rounds through it, lo and behold one side of the pivot was cracked. I contacted the seller (wolverine supplies) and they made it good but it soured me on the whole AR180B polymer lower to this day. If Armalite had of made the lower from stamped steel like they did the upper it would be on my Never Sell list. Obviously other people’s experiences may vary, this was just mine.