"Gas efficiency is absolutely insane with these magazines, only con is that when games are over you have to make the choice of removing them early or waiting until your next game to empty them. I don't have a proper estimated but I think one cartridge goes through about 4 full mags, right on par with elite force, and maybe more. Only problem, is that for some reason this makes the P09 dry really fast, and makes it lock up partway with the slide cycle, or make the gun just fully lock back the slide even when the mag is not empty. It's completely fine though, just lube your gun well once that happens if you have a break, and you'll be fine. You can just pull the slide back a bit and it'll rack forward like normal. Just don't ignore it, it's needless wear you can avoid. This gun needs plenty of oil with these mags, so I assure you, DO NOT skimp on it, it'll only backfire. Anyway, these mags were pretty darn great, just avoid overfeeding too much, it may cause this one weird jam that is really hard to fix, and your gun will keep dry-firing while your bb's are not feeding during this jam, and I think I may have needlessly damaged my gun, as this happened while I was using a tracer, and merely assumed it was malfunctioning instead, so learn from my mistakes, and always put in a reasonable amount, as it has plenty f space anyway. Btw, if you are new to airsoft, and don't know much about gas mags, DO NOT put oil the in the feeding/bb containment area of the magazine like it said in the manual of the original gun, it will impair the function of the mag over time, so just don't touch it. (I didn't do this, I just knew already)
Final Note- All in all, this magazine is really nice, and actually better than most, including the wider bottom for easier bb access, but not a full 5 star due to it's minimal issues.
Side Note- I would recommend using 2 co2 and one green gas mags in an airsoft game, or two of each if you can, as it would basically fix all the issues, and merit this magazine a 5-star status.
"I have 5 of these mags and for e most part they perform very well. The lowest temperature you can play with these are at least ~70 degrees farenheit. One mag puncture gas relase broke and is now stuck and i do not know how to fix it. The base caps are very fragile. One drop and they are broken. Otherwise they have a really good kick, sometimes some mags have less kick and i do not know why. But overall i would say these mags are decent.