Just picked up my new '18 GMC Sierra SLT crew cab truck.   My previous two trucks were an Escalde EXT and an Avalanche.  I love the hard covers that are stock with them.  3 piece, individually removable, waterproof and you can walk on them.  Very durable and work great  Also, they are flush with the top of the bed rails. Who makes one that is similar?  Nothing metal.  No one-piece covers.  No soft covers.  The Back Flips seem to be the closest, any other alternatives to that?