This. is. amazing! These magazines work just as well as the real deal Lonex version and fit well in my KWA M4. They are durable and very helpful not to mention, cheap. Mine lasted me about 7 months but the cord at the bottom cut through some plastic making it more difficult to grab. Other than that these are simply outstanding. I did a video review so here's the link:
http://www.youtube.com/watch?v=etcm4VzEIWc
Cheers!