Copper TriLayer, Thick Core of Aluminium, Even Cook: Casserole/Saucepan Lid Made of Copper, Aluminium. Stainless Steel: A range of top quality Casseroles/Saucepan lids manufactured from outer Layer 7inch Saucepan/Casserole Lid: C106 Copper 1.88mm thick, InnerLayer 7inch Saucepan/Casserole 304 Aluminium saucepan 0.2mm thick