You have more space to place your dish in a microwave with 1 or more rack levels. Put the rectangular rack high or low in the microwave and easily place a rectangular casserole on top of it. When a combi microwave has 2 or more rack levels, you can prepare different dishes at the same time. You can, for example, bake cookies and cupcakes or 2 pizzas. A solo microwave with rack levels isn't suitable for baking, but is useful when the microwave has a grill function. You can use the rack levels to decide at what distance you place your dish from the grill.