After 2 decades of not having a cover on the back of my trucks I decided to look into it again with the Tremor and decided on the Undercover Armor flex. Almost the same as the BAKflip mx4 but has 5 year warranty vs 3. I really like the Retrax pro in the same way that I really like the 6.7 but I truly didn't need it. I wanted a hard cover, that I could open in increments. I wanted to be able to use a majority of my bed space when needed and all of it without a lot of hassle. Waterproof would be nice but I really would just like to keep leaves, snow and crap like that out of the bed. I will never leave valuable stuff in the bed so locking would be nice but not critical. It will show up later this week and I may install it over the weekend.
My 2 cents.