The HydroHug Hot Water Therapy Pillow works like a hot tub without getting wet! It’s a versatile, lightweight tool that can be used to relieve muscle pain, soreness, and stress. They’re durable and can withstand significant weight. The pillows are easy to fill with hot or cold water. Each bag is constructed of a soft, pliable, lightweight polymer plastic. The secure, leak-proof lid, “pops” on and off easily. They come in three sizes to accommodate different needs.