If you're asking about our horse-trailer windows, I feel they've worked out fine for us.
The big caveat with them is they're not designed for the U-Haul
window-recesses. So I trimmed material both from the camper window opening AND from the brand-new window flanges. 2 Things most folks wouldn't want to do.
And then I glued them in place with automotive windshield polyurethane---a wonderful & durable material than can be incredibly messy to work with..... so, a 3rd caveat.
Hence, I don't promote our path, even tho' it worked well for us.
Likewise, even though I loved driving old air-cooled Beetles for years, I wouldn't recommend them to hardly anyone........'cause you have to tinker with them all the time........and you still end up with an only-marginally-safe vehicle, that gets mediocre mileage, with precious few creature comforts.