This is the pillow that uses water-filled and foam layers to help improve sleep and reduce neck discomfort. A study by Johns Hopkins University found the water-filled bladder to be superior to other models at relieving neck discomfort and improving sleep. A water bladder inside the pillow can be filled to a preferred level of firmness and accommodates the contours of your head and neck as you move to provide continuous customized support and comfort. The top layer of cooling memory foam is cool to the touch and allows air circulation, ensuring you are always lying on the cool side of the pillow. The bottom layer of memory foam creates support to enhance neck and head comfort when reading in bed or while sleeping. The 200 thread-count cover is 100% cotton. 25" L x 18" W x 4" H. (3 lbs.)