I know that there are a lot fan of this spray in bed liners. After I checked our 2016 6'5 bed and the really big gabs all over (bigger then our 2016 F150), I think it has enough drainages to release any moisture underneath a drop in bed liner. I'm sure with the proper maintenance, (cleaning underneath the drop in bed liner every month) - the bed will be OK. If you only drop it in and never check or clean underneath, there will be lots of rust showing up. But that is the same with a spray in bed liner. If you never check all over the bed, you can get in trouble too. There is a point that some people complain about lose spray in bed liners. I did secure my drop in bed liner with Velcro like the bed rug in our F150 (who has a factory spray in bed liner too). The material of the RAM drop in bed liner is more like a rubber/plastic mix and not pure plastic feeling. We also have tonneau covers on both trucks. It's with everything in life. If you don't maintain and service cars, trucks and tools they start rusting.