With the news of Magpul’s Glock magazines, the Elite Tactical Systems Group magazines got drowned out. ETS is making transparent polymer Glock Magazines. They are expected to be released in April and they are making different size magazines for 9mm.
Unlike the Magpul magazines, the ETS mags will be compatible with any aftermarket glock base plate, so you could use round extenders if you wanted.
The obvious benefit over the Magpul Glock mags is that the ETS mags are transparent thereby allowing you to count your rounds in the mag. The Magpul mags only have a hole for the 17th round in the Glock 17 compatible magazines. Why is counting your rounds important? Options. Not everyone shoots their pistols like everyone else. Some people dont care how many rounds are left in a magazine and will just go to a fresh one. That is one way to shoot. Another is a competitive aspect. IDPA and USPSA in particular. There are divisions that only allow 10 rds or less in a magazine. After a course of fire in USPSA, you may end up with rounds still in your magazines. It is much easier to top back up to 10 with the ETS magazine than the Magpul magazine. It is a preference and does not detract from either product.
One thing the Magpul Glock mags beats the ETS mags is in price. The ETS mags are estimated to be $20 MSRP.