As for the 3-layer structure the pillow goes with any sleeping position (side, back and tummy sleeper). The height is adjustable and therefore ideal for any sleeping position. You get the maximum adjustment and can choose your preferred top side. For Side Sleepers: As the gap between the head and the shoulder needs to be supported, we recommend you use all three layers to give you the perfect balance of comfort and support. For Back Sleepers: If you are a back sleeper, we recommend using two of the three layers. In choosing the upper layer, of course, you are free to decide which upper layer you prefer. For Tummy Sleepers: For those that sleep on their stomach, we recommend you take all but one layer for the ideal height. You are free to choose which layer you prefer.