Description: These Hard Folding Tri-Fold Tonneau Covers provide quick-and-easy access to the cargo area of your Sierra while providing protection for items in the pickup bed. Contact your GMC dealership for more information. Tri-Fold, Hard Folding Tonneau Cover in High-Gloss Black for 8' Long Box. The cargo in the bed of your truck will be secure with this Hard-Folding Tonneau Cover. It has a rigid panel design that opens in equal sections and allows for quick and easy access to your cargo.