Pop-Tarts is the bran name for a flat rectangular toaster pastry approximately 3 inches (7.6 cm) by 5.5 inches (14 cm) made by the Kellogg Company. Pop-Tarts have a sugary filling sealed inside two layers of rectangular, thin pastry crust; each layer of this crust is about 0.1 inches (2.5 mm) thick. Most varieties have frosting, but some do not. They can be eaten without being warmed, but are often warmed inside a toaster. They can also be microwaved but only for a few seconds or else the filling hardens into a solid. Recently, certain varieties have been marketed as tasting best when left to cool in the freezer. They are usually sold in pairs inside foil packages, and do not require refrigeration.