It's Easy! Simply open the colorful Little Hotties polybag and remove the warmer package. It's as simple as that, the warmer will begin warming in a few minutes. The warmer will continue to warm to an average temperature of 120F and in some cases can reach a high termerature of 150F. Little Hottie Warmers will work best in an enclosed area such as a glove or pocket. Each unit measures 2.25" x 3.75" and lasts up to 8 hours.