This unique hand warmer is referred to as "crystallization type". It is activated by flexing a small metal disk inside the hand warmer and stays warm for 15-25 minute. Can be used up to 300 times.To reuse, submerge in a pot of water and boil on stove for at least 15 minutes, or until filling is completely liquid and clear again. Complete instructions printed on item. Complies with CPSIA, Prop 65. 3.1875" L x 3.75" W x 0.5" H

Colors: Royal Blue, Red

Sizes: 3.1875" L x 3.75" W x 0.5" H