Roll N Lock M-Series Truck Bed Cover for 04-08 F-150 SuperCab/SuperCrew; 2006-08 Lincoln Mark LT 5.5 Ft. Bed Model LG170MRoll N Lock M Series Locking Retractable Truck Bed Cover for 2004 2008 F 150 SuperCab SuperCrew; 2006 2008 Lincoln Mark LT 5. 5 Ft. Bed Model LG170M Roll N Lock M Series is the most advanced retractable truck bed cover made, has redefined the rules for truck bed security. From its retractable function, which permits opening or closing in seconds, to its rigid, vinyl over aluminum laminated construction, this hybrid cover offers everything other covers