They seem to work well enough, tougher than trash bags and easier to see whats inside than nylon stuff sacks, for storing extra clothes and winter wear in a vehicle. I'm often impressed by the general level of quality. The vinyl is usually nice and thick. The unit is often well assembled, stitched well with a cloth binding tape, or welded strongly. The zipper is typically sturdy if not exactly overwhelming sturdy. Zips may be the one common weak spot. They all seem to be squarish shapes that stack well and fit more easily in a trunk or behind a seat.

I've entertained the notion of using some thin flow-able silicone, commonly available as windshield sealer, to try to seal the seams and stitching to make them more water tight. But in a vehicle they seem waterproof enough to shed casual splashes and blown in rain, and easily keep dirt and dust at bay.

You're not going to storm Everest with them but they do have uses. One use not mentioned is as equipment covers. Typewriters, anyone here still have typewriters?, sewing machines, and printers can all benefit from use of a cover to keep dust and dirt off and these thick vinyl boxy units work pretty well if you get the right size and cut off the flap end. Purpose build covers for these things typically goes for about $20. Free is good. Sure beats tossing an old towel over the equipment to try to keep the dust off.