||both stock marui mk23 mags I had started leaking from the bottom.
propriety design of stock mags make it difficult for disassembly/repairs (but not impossible) do to a one way pin.
I opted for newer replacement mags, and got two of these for the same as one stock mag would cost.
1) fits perfect.
2) noticeably more powerful, as well as more willing to accept green gas.
2) half price as stock.
1) bbs do not load/fit from the bottom like they are supposed to. To be able to load bbs quickly from the bottom you will need to dremel a little bit out so that they may pass through. Not a big deal, but if you don't have a dremel than good luck speed loading the mag.
2) It does not have trades such as "hk", and does not look as nice neither.
all in all these mags get the job done, definitely worth buying for sure.
Rating: [5 of 5 Stars!]