This is a HEXMAG known as the HexID, model HXID4-AR-GRN.
Hexmag knows just how important it is to safely" quickly and efficiently identify ammunition calibers" which is why they pioneered the first ever colored rifle ammunition identification system - the HexID Color Identification System. Color-coded magazines can be changed without tools" in under 1 minute.
Features:
Helps Easily Identify Magazines
Safely Separate Calibers
No Permanent Markings