ThermalMAX microwavable heat packs retain heat for up to two-hours per use when used as directed, and provides effective comfort and relief from pain. Perfect for arthritis, stiffness, soreness, reducing swelling, and more. The microwaveable heat pack will fit perfectly on your back, shoulder, neck, hip knee, ankle, elbow, and wrist. Other relief products from the makers of ThermalMAX microwavable heat packs include CryoMAX Ice Packs and TriCalm Steroid Free Itch Relief Gel.