There is a caveat to the water tight claim. It's going to need rubber gaskets where it hits the tailgate, and internal drains along the rails where the tonneau slides. That will never be perfectly water tight, you will always have some moisture in there when you open the tailgate. You can look at similar internally installed tonneaus from vehicles like the Avalanche, Ridgeline, etc. The only way you get 100% falling rain protection is with a lid....like a single piece fiberglass Tonneau that lifts up....and we all know how crap those are to use for anything but putting groceries in back.