This jig makes easy work of re-wrapping 18650 batteries. Just insert the heat shrink in to the jig, using a utility knife or razor blade cut the heat shrink to length. Remove the heat shrink from the jig, re-wrap 18650 battery. Place newly wrapped battery into the round height jig, this part of the jig will position the battery center of the heat shrink. Using a heat gun re wrap your battery