GrillGrates are the No. 1 ranked grill surface in America! Made in the USA from hard anodised aluminium which will never rust, they have patented raised rails with a flat base plate interspersed with holes for airflow. It is this design that amplifies the heat and eliminates hot cold spots, whilst the bottom plate protects food from flare-ups. In addition, drippings are vaporised in the valleys adding flavour and moisture to the food. For an added boost of smoky flavour, you can sprinkle some wood pellets in the valleys. The raised rails create perfect sear marks on food, however, you can reverse the panels if you wish to use a flat griddle surface. Through use and over time the GrillGrate will season, enhancing the non-stick properties. This GrillGrate set is compatible with the Web Spirit 300 Series and pre-2007 Weber Genesis grills and is designed to replace the existing stock grates. If using this set on a new model Spirit, you will experience about a 2 gap.