I just received this and used it on my SMC 9. It fit like a glove and hooked into the HPA system no problem. I received this as a Christmas gift and have shot about 700 rounds thru it in the back yard. Doesn't take long in full auto lol.. So I have not used it very long. From how it performed I see no issue with it holding up in the field. It seems very well made. Also all my M4 mags that I used fit and worked great. 1 was a BAMP mag and one was a Wolverine mag that came with my MTW the other mag was one I grabbed out of my bag. Very excited to have turned this gun into an HPA and being able to load a large amount of BB's is really what I was looking for. I also don't have to carry the heavy 50rd mags that come with it. I have 3 of them so I probaly save 5lbs which is a bonus in CQC. I was waiting for the drum mag to come out and then I saw this. I already have a M4 drum mag. Next step will be to plug in the drum mag. This was a great purchase.