Cybergun have released the 24 BB Round magazine for the M&P 9 GBB. It's metallic and slightly grainy magazine which gives it a realistic feel but it's about how well it is used while shooting which is perfectly fine!

Apparently Cybergun made two versions of the M&P that can run on co2, if you have the one with thumb safety, this would not fit, please get KW148 instead.