Grabber Foot Warmers are single-use air-activated heat packs that provide 5+ hours of continuous warmth for your feet. Simply open the package, slide into the bottom of your boots or close-toed shoes and let the heat sooth your cold or aching feet. Grabber Foot Warmers are specifically designed for use inside a shoe or boot where oxygen is restricted. Do not trim or peel. Place the fabric side up and white side down.