I couldn't say what they are made of with any certainty, but a few of my MAMS have bulged to the point that I'm not comfortable attaching a can (if I could?) after using them on some belt fed MG's. The Triple Tap does seam to go longer in use without bulging, but the MAMS does seem to help control the platform better than the Triple Tap.
I'm really curious to see an all inconel version, or in that a can that handles a belt gun as well as the NT-4. I'm hesitant to to hang some of the newer KAC cans and others on some hosts. The NT-4 is like a tank, seems to out live some other brands MG only cans similar in size.