We planned to coat our Sierra Denali's bed with a composite liner. Instead of spraying the composite material over the bedrails, we felt plastic covers were a more attractive option. Past experience with low-end aftermarket offerings has proven that the bed rail protector kits from GM generally fit best and install easiest. While shopping for Assist Steps at GM Accessories Zone, we found that our Sierra Denali's factory-installed bed rail protectors (No. 17802473) are available for $109.