There are two options out there: tools powered by replaceable batteries, and rechargeable curlers that use a USB charger. I prefer the rechargeable kind!
Look for curlers that are covered with a thermal protective cap or heat protection groove. Other features like uniform heating, insulated brushes, and a heat protectant layer can keep your eyes and lashes from being burned or injured.
A curler with variable temperature options and heat settings is ideal. Thermal protection slots control the temperature and prevent overheating to keep it at the optimum temperature.