Cakeboard Marble Round Extra Sturdy Ø25cm The Cakeboard Marble Round Extra Sturdy Ø25cm has a beautiful marble print. The diameter of this coaster is 25 centimetres and the thickness is about 4 mm. A cake board not only looks super nice, but is also very functional. In fact, the board is very handy to put in a cake box, to prevent the box from getting damp. Or put the cake board down as a coaster on a cake tray. You could also reuse the coaster, just clean it after use.