• 300rnd Capacity
• Polymer mag design
• For M4/AR-15 AEGs
If you need more ammo between reloads, a high-cap magazine will do the trick! The Delta Armory 300rnd High-Cap Magazine for M4/AR-15 AEGs is styled after a famous polymer magazine, making it well suited to any modern M4/AR-15 AEG build. As with other high-cap mags, the winding wheel is located on the baseplate and the fill window is on the top. 
To load the mag, simply open the hatch on top, pour your BBs in, wind the winding wheel 5-10 times, insert the mag and you're ready to shoot! If you prefer putting down rounds over reloading, a couple of these will give you what you need!