Soft, "frost-free" cover. Hot/ cold pack can be applied directly to skin. Sized to fit nearly anywhere you need hot or cold therapy. Helps treat strains, sprains, tendonitis, and other injuries. Store in freezer until needed. Heat in microwave. Non-toxic, biodegradable gel. Large packs are suitable for the upper or lower back, knees and thighs. Tri-Sectional Packs are suitable for the upper back, shoulders and up the neck.