These shrink wrap PVC battery skins don't just look good, they can also help protect your 18650 battery.
Batteries must always be in good condition and have their wraps fully intact. A battery can be dangerous and cause a short if the wrap on the battery is torn or damaged in any way.
HOW TO REWRAP BATTERIES
Here are a few simple steps to follow:
Take off the existing wrap from battery*
Put the new wraps around the batteries
Using a heat gun or hairdryer, shrink the new wraps onto the batteries.
* Do not put the new battery wraps over the existing wraps. The wraps are a specific thickness to ensure efficient heat dissipation so if you put a wrap over an existing one, you may reduce the amount of heat that a battery can get rid of therefore making it dangerous.