This is 20 gauge stainless, used to cover the top of the hopper. It still allows the factory hopper lid to close over the top of it, including the knob (yes the knob fits under the lid).
This mod keeps the creosote down in the hopper, not on top of the hopper or on the lid. This helps a lot to keep the factory lid sealed. The mod comes with enough gasket to put under the hopper cover, as well as both upper and lower grill doors. Mating the rubber seal of the factory door with the gasket makes for a much better seal than just the rubber.
This helps keep heat further away from the top switch as well.
included in kit: Hopper Cover, 15ft of Fireblack gasket ($65)
Hopper Cover only is also available ($45)
choose between the two in the drop down menu above