Herter's Inc. of Waseca, Minnesota. Hand warmer usage directions: remove top of case, light wick fueled by the fluid stored in the case below the wick, extinguish the wick and replace vented top. The hand warmers fit comfortably inside a pocket, providing heat for up to 12 hours a day. The intensity of the heat is adjustable. Waseca business: Herter's Inc. Herter; Herters; Herter's.