Hot Tub Pillow: This booster seat cushion is perfect for hot tubs, bathtub, inflatable swimming pool and spa. Bath Tub Seat : Made of high quality heat resistant material, covered with gauze which can prevent slip. Easy to Use: Easily filled using standard hose nozzle or fill by jets in spa. The suction cups prevent hot tub cushion from floating or moving of your hot tub seat. Hot Tub Pillow: Firmness and size can be adjusted by the amount of water used.Drying the tub before use will help the suckers stick better. Size : 15.35"(lengh)*15.35" (width)*5.9"(height)