Safariland is known especially among law enforcement officers for it's retention holsters, and these are about as good as it gets.
These holsters specifically made for Glock Pistols (See variants for model) feature the ability to effectively "lock" the gun in place and add new "levels" of retention. To save you from the agony of having to browse the god-awful Safariland website and decipher it's Da-Vinci-code-tier product acronyms & numbers, here's a quick crash course for dummies on everything you need to know to pick a holster:
Retention Level, ALS vs. SLS, & "Sentry"
ALS locks the firearm into place immediately upon holstering, and SLS provides extra security with a rotating hood.
For retention levels, these are level III and IV respectively:
III - when the gun is holstered, the "sentry" blocks assailants from pressing the ALS release button, and it may also require the user to flip a hood away and press a button to release the locking mechanism & un-holster the firearm.
IV - when the gun is holstered, the "sentry" blocks assailants from depressing the hood in order for it to be flipped open. then just like level III, the user presses a button to release the locking mechanism & un-holster the firearm.
Both of these make it very difficult for the typical assailant to quickly swipe your firearm, which is why level II and IV are widely regarded as being excellent for duty, corrections, & other open carry uses.
This one is as the name implies.
Does your Glock have a light on it? If so, the light bearing holster provides extra room for the firearm to fit with common lights such as the TLR-1 and Surefire X-300. In some cases, this holster can also fit Glocks with smaller, flush-mounted (in the case of a glock 19) lights like the TLR-7, with just a bit of extra wiggle. Still completely serviceable.
STX Plain Vs Basketweave
We've all seen the ugly uniform codes the boys in blue have to abide by, and basket weave material is one of the odd quirks that continues to be a major part of it (somehow it allegedly makes their gear "less intimidating"?).
"STX" is their rugged polymer material that makes up the construction of the holsters, and neither plain nor basket weave is stronger than the other. If you really hate how it looks, a good spray paint job or Cordura wrap can make it perfectly fit with your kit.
Picking your holster
Read all of the above? Good. Simply pick whichever holster matches your desired retention level, "RH" for right hand, "LH" for left hand, Glock model number, & finally, material style.
Unfortunately, none of these are red-dot compatible.
A note from Ivan on fit:
as mentioned earlier, flush mounted lights on 17s and 19s will fit in the light bearing holsters. In addition, 19s will fit in 17 holsters, and 17s will fit in 20/21 holsters but with a little bit of wiggle (the 20 and 21 are the 10mm models, and have a bit more thickness).
Holsters are in excellent condition, with minimal use. All hardware is present and functional. Light bearing models may be missing light endcap, but this isn't necessary for the function of the holster.