The Hiti is a round, reusable gel-based heating pad for the pocket of your jacket. Clicking the metal plate makes the gel react and release heat for up to 1.5 hours. After use, place in hot water until the gel has liquefied. It is then ready for further use and provides up to 90 minutes of comfortable warmth. Each pack contains two heat pads. Its round shape means it fits snugly in the bottom of a gas canister, therefore extending the cold-weather use of many gas stoves.