Magpul is surely on a roll with their PMAG. They're the most popular magazines among airsoft players who use these for the TM-compatible M4 AEGs and Gas Blowbacks. The PMAGS are the most durable magazines made with polymer, and many users attest to its durable, having driven over it and still fires. Furthermore, with its polymer construction, it is light, as compared to the steel magazine, allowing for more magazines to be loaded by the soldier and increasing firepower.
The EMAG is still part of the PMAG family, with a Maglevel, which is a window for which you can peek into the magazine to find out how many rounds are remaining. Designated as an Export Magazine (thus, the EMAG name), it is made mainly for other rifles that take STANAG-compatible magazines but have different magwells. This covers the FN SCAR, SA80 (L85), and the HK416. It has a slicker side with anti-snag feature as compared to the ribbed PMAG. The PMAG ribbed side is designed for enhanced grip.
Recently, Magpul added a second window to the EMAG, which for ambidextrous users, means that they can see the bullet load level in their magazines from both sides. Furthermore, they recently bagged a million orders for the EMAG from the British Army according to the Military Times.
That's a lot of magazines, but in accordance with the Urgent Operational Requirements (UOR) of the MOD, which in terms of infantry equipment, they want to double the firepower of the squads, which are 8-person infantry sections. The EMAGs are lighter and with their Impact/Dust Covers, they provide protection to the magazine, especially in rocky and dusty conditions in their present operational theatres, which means Afghanistan. The covers can be inserted into the bottom of the magazine when the magazine is in use.
The magazine spring is has an indicator coil painted in bright orange for the soldier to look for when looking into the MagLevel, to note when the magazine is about to get emptied while in use. For armourers and quartermasters, they can know that they're issuing fully loaded magazines to the soldiers, rather than issuing half-empty ones, avoiding leaving the soldiers short-changed in their bullet load.
The double window Maglevel EMAG will soon be available to other users when existing single window EMAG stocks run out. For now the British Army gets first priority for this latest EMAG iteration. Which means also that airsoft players may need to wait a little bit more for Magpul PTS EMAG double window airsoft version as soon as their stocks also run out.