Yes all mags (of the same type) are 100% interchangeable between brands. A little bit of filing or taping may be required (tolerance issues) but for all intents and purposes you can use any brand mag in your gun.
NOTE*: A SystemA PTW mag won't fit in any other AEG, GBBR mags don't fit in AEG's (and don't fit in other GBBR's sometimes because of different systems) and GBB Pistol mags are usually brand specific (again because of different Blow Back systems, a TM mag will fit in KJW (A TM Clone) but not KSC/KWA. KSC and KWA mags are interchangeable (because they are basically the same company, getting their OEM parts from the same factory)).
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