The 12 inch vertical dome is misleading. The side is 4 1/2 inch. It will hold a 2 layer 9 inch iced cake well but I purchased this because I thought it would hold three layer cakes. It’s a heavy lid, well made, looks nice in the dining room. I saw a true 12 inch dome lid at a store but the glass was too thin. I knew it would soon be broken. I wanted pretty and functional. This met that criteria. Works well for a small punch bowl. Picture shows two 9 inch cake pans with the tops together to show how an iced two layer cake would fit.