I got a Truxedo Sentry CT. It was a huge PITA to install on my Rambox bed with rails. I had to loosen all of the rails and have someone stand on them to get the Truxedo rails to sit flush with the Rambox tops. The weather stripping on the Rambox doors goes in every time I open them. The rubber flap over the tailgate sunk down within about a week, and now I have to hold up the cover to close the tailgate. The cover is also extremely hard to snap shut. It flaps in the wind on the interstate.I ended up with the BAK Revolver X4S and I am pretty impressed with the fit and the quality of it. It went together rather easily, seems pretty stout and still allows the use of the rails and tie down anchors that came with the Rambox. Here's a couple pics that I snapped. I really like the way the rails for the cover slide into the factory Rambox rails. Install tip for those that end up with this model, mark the washers then loosen the rear 2-3 bolts a bit to allow more room for the seal to slide in.
Would not recommend this one