Clones of the Socom Gear Lancer L5 Advanced WarFighter M4 magazines by Kublai in opaque black. They're advertised as 180rd and I find that's pretty accurate, though I do find in my G&G CM16 the first 10 rounds go everywhere if you try to fill them completely, don't seem to have the same problem in my Ares Amoeba CCC though
Has a window at the top where you can see BBs if there's at least 100ish loaded which is a nice little feature (see photos). Decent feeling plastic, easy to get the spring out for cleaning.