Line-X, Rhino, and Perma-Tech are the top ones. You can get the do-it-yourself ones at the autoparts stores but they aren't near as good and don't hold up as well as the professionally done ones. You could also get a Bedrug if you want something a bit more flashy and show looking. They are very durable and I've heard of guys haulin' engines and everything with them in the truck. Waterproof, fuel, chemical, etc. proof.
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1994 Red SVT Lightning #2019