The "Porcelainized Cast Iron Cooking Grids" are replacement or upgrade cooking grids designed for the LEX 485 gas grill. These cooking grids are made of porcelainized cast iron, which is known for its durability and heat retention properties. They are ideal for creating sear marks on your grilled food and can last for a long time when properly maintained. If you have any specific questions or need further information about these cooking grids or how to replace them, please feel free to ask, and I'll be happy to assist you.