These high performance 18650 lithium ion 3.7V batteries offer high performance and long life from a compact package. This model has in-built protection features to ensure safe operation at all times. These include over charge, over discharge, short circuit and over current protection. Dimensions: ø18.6mm x 69.9mm Lithium-ion rechargeables offer excellent properties for use in consumer devices, including excellent energy density and low maintenance. Lithium-ion do not suffer from memory effect and possess no regular cycling that batteries often require to extend their service life. Common applications for 18650 cells include: Laptop computers LED flash lights Electric vehicles Power tools Converting AA or AAA powered products over to higher performance (providing voltage matches).