Thanks. What was changed for the RollX HD? There isn't much info online about it.
From the BAKindustries site,
Roll-X HD
Roll-X HD is new for 2014 and represents another leap forward in BAK Industries tonneau cover design. The front section of the cover is larger with dual mounting bolts for a more secure mount to the truck. The rear of the cover has also been extended to allow a more forgiving fit with trucks that have drop in plastic bed liners while eliminating the need to modify or trim the liner.
The largest advancement in the Roll-X HD is the larger locking rail. Now the Roll-X HD has over twice the locking ability so if you go off road or if you just want a cover that is more secure then Roll-X HD has the features you need most. Roll-X HD is stronger and more secure while still offering all the access and provides for mounting the most accessories than any other hard cover design.
And this about the Roll-x xt
Roll-X - XT
Roll-X XT is yet another advancement in Roll-X rail technology. BAK Industries has changed the game yet again. The new Roll-X XT model comes complete with a new accessory mounting channel inside the bed where a host of new accessories can be mounted. Now your Roll-X XT can accommodate The BAK Box 2, BAK Stop cargo divider, BAK Bike Rack, Tie Downs, Mag Lite clip on mount with swivel for illuminating the bed, side box options and more. The innovation at BAK Industries never stops and the Roll-X XT is proof that you can get the most out of your truck and mount even more of the accessories you need most with this new Roll-X XT design.