Here is the BAKFlip MX4 sized for the Chevy Silverado / GMC Sierra 1500 (2014-2018, plus the 2019 Silverado 1500 LD and Sierra 1500 Limited) and 2500 HD / 3500 HD (2015-2019) with the 6'6" bed. That box runs about 78.9" along the floor. Revised EPDM perimeter seals and tight-fit clamps help keep weather out, and drain tubes carry off water that reaches the rails. BAK calls the MX4 America's best-selling truck bed cover, and the Gen 3 version adds re-engineered locks and a longer dual-action tailgate seal. The textured matte black cover sits flush with the bed rails and is rated at 400 lb spread evenly. Fitting it is straightforward: it clamps to the bed rails with no drilling, following BAK's Chevy/GMC sheet, and BAK calls it a Level 1 job of 30 minutes or less. The 2019-2027 Chevy Silverado 1500 / GMC Sierra 1500 (current body) takes BAKFlip MX4 448131. The warranty is BAK's 5-year limited coverage.