ColdStar - All-purpose Hot/Cold Cryotherapy GelPacks (Non-Insulated) are reusable gel packs that are ideal for recurring hot and cold therapy needs. Microwave the gel pack for warm therapy or place in the freezer for 2 hours before application for cold therapy. The soft freeze gel stays flexible when frozen, allowing the cold pack to conform to the contours of the injured area. For either hot or cold therapy, the ColdStar non-insulated all-purpose gel pack provides soothing relief to any part of the body suffering from aches, pains, or stress. Compares to Jack Frost.