Great product for a standard build - CMMG, Inc Receiver Extension Kit, Carbine Length

I've used these for two builds so far, they work as-advertised. I prefer to buy the extension tube, spring, and buffer together for basic builds so I don't need to do the leg work or forum research to find an optimal combinations for a given rifle (you also tend to get a better deal in my experience). I did swap a third one of these out for an anti-tilt buffer on a lower that I wanted to pair with a piston upper, but that is sort of a special case where the upper was has a notorious failure mode to with special components. I'm happy with this extension tube set.