UnderCover Flex 16-24 Titan 6'7" Model FX51016UnderCover Flex 16 24 Titan 6'7" Model FX51016 Introducing the next generation of folding covers the UnderCover Flex folding cover. Flex combines the best of both worlds, the security of a hard locking cover and convenience of a soft roll up cover. Constructed from the best materials available, Flex will withstand the abuse Mother Nature throws at it and keep coming back for more. Low Profile Ultra low profile design rests inside the bed rails