Coghlans Handwarmer - Set of 4 Keeps hands warm in pockets or gloves for up to six hours Activates when exposed to air Average temperature 140 F, maximum 155 F Keeps hands warm in pockets or gloves for up to six hours. These are not just for the outdoors. Measures 3" x 4" (7.6 x 10 cm). Wt. 1 oz. (28 g).