The River Raider Evap Skid is formed from 3/16'' steel like the rest of our JK skid systems. It features grade 8 hardware and a simple bolt on installation in the factory evap mounting location, with no cutting required. Available in bare steel / aluminum or with a black satin smooth finish. Our aluminum skid system weighs approximately 1/2 the weight of our steel skids. UHMW stands for Ultra-High Molecular Weigh Polyethylene and these 3/16" thick panels are specially designed for sliding over rocks. They can be used with the steel skids, but are not really necessary with the steel. We do recommend them if you are getting the aluminum. Our aluminum skids are made from 1/4" material and will protect your system, but they will get scratched if you wheel them hard so the UHMW protects the aluminum and helps them to slide over the rocks instead of getting scratched up.