Propper has started several new apparel collections earlier this year with these STL I Pants being a part of the LS1 line. I don't know what any of those abbreviations mean, but the general design theory on the LS1 line is to combine tactical and athletic ideas which seems like a pretty good idea. Overall they fit a good middle point where they don't quite scream tactical man yet have more usable features than the more covert designs.
For notable features the main fabric is a nylon spandex mix. Although not a bad material by any means they try and make it sound fancier than it is. It isn't very water repellent and the stretch is very minimal. I also seem to get more pilling on high abrasion areas compared to say a pair of 50/50 nyco material pants. That said it is an overall comfortable and reasonably breathable material.
Usually the key to pant usability comes down to pocket layout and the STL I does pretty good there. Starting with the cargo pockets they are slanted a little to help with access and are non-billowed to stay lower profile. Opening with 2 pieces of velcro the interior has 2 extra dividers for pistol mag sized item organization. I would have preferred these dividers be on the side closer to one's body to reduce flopping even further during heavy movement, but being on the away side they are likely easier to access. The hand pockets are a fairly standard size, appropriate for looks yet not exactly roomy. As a nice touch the opening edges are wrapped to give abrasion resistance for clips on gear like knives and flashlights. On the right side is a bonus small change type pocket which can be good for smaller items to reduce item fishing. Some folks will dig it, however it does get in the way sometimes on my personal wallet insertion. There is a frontal thigh pocket on the left side, which works out good for holding my smaller sized smart phone. I'm not sure if making it look lower key is the excuse for only having one, but I wish this pocket type was also on the right side as they are very handy for quick access while sitting / driving.
On the back side the pocket party continues, a nice combination of quick access deep pockets with small velcro semi-closures and smaller zippered pockets above them for higher security options. Fortunately the zipper sliders seem to stay out of the way so there aren't comfort issues when closed and the dual pocket layout should cover the vast majority of user butt carrying needs. As a sneaky bonus there is a center stash pocket which could be a good place for money or E&E items, yet if you want to get creative it is big enough to partially stash a pistol.
As for other small details the pants sport a zipper fly with metal snap and backup traditional button. This layout makes for good fly convenience with the button helping out any failures allowing one to make do till they are able to fully repair.
Overall I think the STL I Pants do a good job at meeting their design goal. They don't necessarily stand out as revolutionary, but that appears to be part of the plan. They cost a bit more than similar pants, so the main sell will be to those who really like the specific pocket layout. For those who like to see an even more low key look, check out the STL II Pants.
Recommended place of purchase: