It is Gas Blow Back Type Magazine.
Fit for Open-Bolt System.
Ready to take CO2 Gas out of the box, offer stronger recoil feeling.
It will not easy to be wear and deform, it was because it made of metal.
Compatible with most WE M4 Series Airsoft Gas Blow Back Rifle Series, also fit to most WE M4 SCAR Series & M16 Series GBB.

Color : Black
Build: Metal
Item Weight with Box (gram) :379
Length :170mm 
Loading Capacity :30+2Rounds 
Bullet Type: 6mm BB 
Manufacturer :WE-Tech