This is a 5 Pack of Arcturus Variable Cap 30/130 Round M4 Magazines. These are easily switchable between a 30 Round Real Cap and a 135 round Mid-Cap. One button easily switches between the two capacities. The magazine shell is made from a single piece, durable fiber reinforced polymer. Mag has a realistic gripped texture and a specially designed follower that makes sure all bbs fire. Compatible with most AEGs on the market, including Arcturus, Ares, Cyma (models with a metal body), APS, G&G, EL, Etc. - Precision feeding mid-cap magazine. - High capacity M4 mid-cap magazine - No rattling during movement like with hi-cap magazines. - All bb down to the last one will feed. - Realistic Weight. Designed to provide a realistic milsim gaming experience. For Tokyo Marui, G&P, Matrix, CYMA, DBOY, Echo1, JG, Classic Army, ICS, SRC, UTG and other compatible AK series AEG.