"Really like these mags. I prefer co2 since it is less affected by the temperature change and shoots @ a higher fps. I have a shortened 170% recoil spring (from a WE g series pistol) and I can get a little over 2 full mags on one co2, however on the second mag the slide does not lock back (could be due to the spring needing more trimming). I suggesting buying a valve tool so you can remove the release valve and lubricate the o-rings to avoid/prevent leaks. The mag holds 31 rounds which I really like and w/ the recoil spring, the gun is extremely snappy and quick shooting, even in 53Â° weather. Definitely recommend.
"The listing states that this magazine holds 24 rounds. It comfortably holds 31 without undue strain on the spring. I can get almost 3 full magazines, about 85 rounds, with one Crosman 12g CO2 powerlet. The plug that came with mine would not thread into the base, but I managed to get it to go in backward. The Allen key hold in the plug goes all the way through, so it is able to be flipped around and threaded in inverted. There is a metal reinforced center, so you don't have to worry about stripping the nylon. I was pretty disappointed that mine was faulty, but it still works, and I imagine this is not typical. I just got unlucky, I suppose.
Recoil is a tad snappier than with propane. Oil, oil, then oil again the valves and seals. This magazine is very finicky unless you keep it wet.
I purchased this for two reasons. One, I wanted a CO2 magazine for my VFC M&P9 GBB. I usually run propane/silicone, but the ease of just popping in a powerlet appealed to me. It's also better in colder temperatures. Two, I am a police officer. I use airsoft for training. I carry a M&P40 with an extended magazine. This replicates the look and feel of the real gun with the extended mag. Since I carry standard mags for spares, I use the gas magazines for spares when using the airsoft pistol.
I haven't had this mag for very long, so I can't attest to the durability of this mag, but it has survived a few drops on hard flooring, and suffered no damage.
If you're looking for an extended capacity mag, this is it. I usually load mine to 20, because that's what my real one holds, but as I stated earlier, it can easily fit 31. The standard mags fit 24, so you're getting a few extra. Obviously, propane is cheaper, but CO2 has its benefits. I like having options, so this was a no brainer for me.
I might post another review once I've had this for a while, but since no one reviewed this yet, I thought it would be beneficial to share my experience.