Ridgid AC840087P 18 Volt 4 Amp Hour Lithium-Ion Battery w/ Onboard Fuel Gauge (2-Pack of R840087 Battery) ONBOARD FUEL GAUGE: You can now see your battery life before you start a job, allowing you to plan accordingly TWIN PACK: This pack has double the batteries, for double the power WEATHER PROTECTED: Operates down to -4 degrees Fahrenheit (-20 degrees Celsius) and up to 120 degrees Fahrenheit (48.89 degrees Celsius) TRIPLE PROTECTION ELECTRONICS: three layers of protection against overcharging, surges, and overheating 4 TIMES THE POWER of standard 18 volt lithium ion batteries