I wanted to relate to you a catastrophic failure of a buffer purchased through Amazon.com, fulfilled by Tactical Military Gear and supplied by Ultimate Arms Gear.
I installed a PRS MAG308 buttstock and the Ultimate Arms Gear USA Made .308/A2-Kit on my S&W M&P 10 and after 13 rounds the threaded plug blew out of the bottom of the buffer and lodged into my bolt carrier. Luckily the only damage was superficial scratches to the bolt carrier and to my wallet.
I contacted Magpul and after looking at the pictures, they feel that the product was substandard and possibly not even made for the AR10. Amazon declined to replace it because it was over 30 days old. Tactical Military Gear refused a refund or replacement stating that they are a 3rd party seller, essentially a middle-man. Ultimate Arms Gear refused a refund or replacement stating that they only deal with wholesalers and business.
Beware of buying buffer kits supplied by Tactical Military Gear and Ultimate Arms Gear, the quality is obviously suspect and the ability to receive a refund or replacement is nonexistent.