This is compatible with MOLLE interface tactical gear (i.e. vests, leg platforms, battle belt, etc.)  This pouch also has plastic reinforced side walls.
Back webbing side is 3x6" (7.6x15cm)

MOD Large Multi-Use Pouch Can Hold:
3x 20 Round DMAG
3x 14 Round DMAG
3x HELIX Magazine
5x M4/M16 airsoft magazines
M249 Magazine  005142