A good list of AEG magazines from CYMA now available at Get Reload. These magazines can fit MP5, AK, G36 AEGs as long as these are Tokyo Marui Compatible, which should mean most brands can readily take these in. No M4 magazines available in the list, but then, CYMA's not known in AR platforms. More details and links below:

CYMA 600rds Hi-Cap Metal Magazine For AK Series AEG

• Replacement of standard magazine AK series Airsoft Electric Gun (AEG).
• 600 Rounds of loading capacity are enough for high shooting rate skirmish airsoft game.
• Plastic construction.
• Large thumb dial on bottom of magazine allow you to wind up the compression spring.
• Suitable for 6mm Plastic Bullet only.
• Compatible with most AK Series of Airsoft AEG Rifle: Tokyo Marui, Classic Army, ICS, etc.

CYMA 220rds Hi-Cap Metal Magazine For AK Series AEG

• Replacement of standard magazine AK series Airsoft Electric Gun (AEG).
• 220 Rounds of loading capacity are enough for high shooting rate skirmish airsoft game.
• Plastic construction.
• Large thumb dial on bottom of magazine allow you to wind up the compression spring.
• Suitable for 6mm Plastic Bullet only.
• Compatible with most AK Series of Airsoft AEG Rifle: Tokyo Marui, Classic Army, ICS, etc.

CYMA 560 Rds For MP5 Long Magazine

• For those who don't like the low capacity standard AEG Magazine
• This Hi-Cap Magazine is a direct replacement of the Standard one
• 560 Rounds of loading capacity are enough for most competition & skirmish airsoft game
• Suitable for MP5 series Airsoft Electric Gun AEG Rifle Magazine (C.37 Black)
• Large thumb dial on bottom of magazine allow you to wind up the compression spring

CYMA 260rds Hi-Cap Magazine For MP5 Series AEG

• Replacement of standard magazine MP5 series Airsoft Electric Gun (AEG).
• 260 Rounds of loading capacity are enough for high shooting rate skirmish airsoft game.
• Plastic construction.
• Large thumb dial on bottom of magazine allow you to wind up the compression spring.
• Suitable for 6mm Plastic Bullet only.
• Compatible with most MP5 Series of Airsoft AEG Rifle: Tokyo Marui, Classic Army, ICS, etc.

CYMA AK74 500rd Hi-Cap Magazine For AK AEG Series

• For those who don't like the low capacity standard AEG Magazine
• This Hi-Cap Magazine is a direct replacement of the Standard one
• 500 Rounds of loading capacity are enough for most competition & skirmish airsoft game
• Suitable for AK series Airsoft Electric Gun AEG Rifle Magazine (C.25 Black)
• Large thumb dial on bottom of magazine allow you to wind up the compression spring
• Suitable for 6mm Plastic Bullet only

CYMA 130rds Hi-Cap Metal Magazine for G36 Series AEG

• Replacement of standard magazine G36 series Airsoft Electric Gun (AEG).
• 130 Rounds of loading capacity are enough for high shooting rate skirmish airsoft game.
• Plastic construction.
• Large thumb dial on bottom of magazine allow you to wind up the compression spring.
• Suitable for 6mm Plastic Bullet only.
• Compatible with most G36 Series of Airsoft AEG Rifle: Tokyo Marui, Classic Army, ICS, etc.