A double sided mattress is one that comes with comfort layers on both sides. The benefit of this for the customer is that you get twice the surface area through a series of rotation and flipping that should become second nature to you as part of the recommended mattress care guidelines. A mattress that can be flipped means you get better settlement of springs and fillings over time which may also prevent dipping over the long term. What's more, a seasonal mattress has different comfort layers meaning that you get a warm layer for the winter, and a cooling layer for the summer, simple brilliant.