For degree of difficulty in production, items with lids rank a "10". Being fired at 2500 degrees ensures the quality and durability for oven use, but increases the risk of torque or twisting of the pieces during this phase of production. To ensure the shape is maintained and that the lid will fit the casserole, the two pieces must be fired together. Each lid and its casserole are then perfect partners and will be boxed and sold together.