72 hour UniHeat heat packs (shipping warmers) activate slowly, up to 3 hours. Their maximum temperature is similar to the 40 hour heat pack. 72 hour shipping warmers reach their peak temperature in approximately 24 hours. 72 hour UniHeat shipping warmers are the best choice for 2nd to 3rd day shipments.
Under “Shipping Tips” found at the top of the home page, please see our complete guide on how to properly use and choose which UniHeat heat pack product is right for your shipping needs.