Perhaps there are still some folks out there who haven't grown a strong hatred for standard lowest-bidder GI magazines, I for one, am not one of those people. All the flaws incorporated with standard GI magazines allowed numerous companies to develop ploy and steel magazines that improve the durability and function of AR/M4 style magazines.
When HK entered the market with a standard capacity (30 round) poly magazine more than a year ago, I would have expected to see it at double or triple the market average of $20 each. What HK did was enter the market at that exact price point, making it a direct competitor to Magpul and Lancer. My admiration of HK pushed me to pick up a few magazines, and I've run them in the Sig Sauer SIG556 platforms since. These are also imported from Germany, they are not (yet) domestically made here in the U.S.
The magazine is translucent, with a grayish tint. Construction is robust, however I have yet to do a crush test to see how they compare to PMAG GEN M3s in this regard. They fit the SIG556 perfectly, the tollerances are great for this platform - they might even be better than anything Sig Sauer has ever tried to stuff in the mag well. Overall the magazine is slightly more robust than PMAGs, spectifically a little more 'square' feeling. The SIG556 has an outstanding magazine eject, it nearly springs the magazine away from the action, allowing the shooter to avoid flipping the action at a full 90 degree angle. The floor plate is one that allows for plenty of drops and abuse, but admittingly I haven't looked into replacements - at $20 price point, who care...buy another.
Range time was the real test, both seeing exactly how it compared to the PMAG GEN M3 and the Troy BattleMag. Loading requires the round to slide along the follower (initial) or at about mid-cartridge for each subsequent round. The real lip where the rounds seat on the primer end is a little more robust than what we see on the PMAG GEN M3s, so this is something to remember. The follower is certainly no tilt, and one will notice the double stack nature of the magazine keeps the bullet end in-line as well along two respective channels - this is like nothing I've seen from Magpul, Lancer, or Troy. Loading is easy, no issues with the magazine locking into place, and it fits quickly. As stated above - there is no side to side or front-back play. Shooting with these magazines is what I would expect, they operate flawlessly and certainly did not cause any failures to feed.
For those looking to break the mold and add something different, an alternative if you will - the HK Poly Mag is a sure bet, especially for SIG556 owners. It adds a new look to the platform, and you won't lose anything in terms of quality, function, or design.
Serpent Tactical offers the HK Poly Mag for $19.99 in the Serpent Store.