But MIL-SPEC Tough: Constructed with satellite-grade carbon fiber, the X1 Carbon is the toughest ThinkPad ever made. In fact, we perform nearly a dozen separate military-grade specification tests—all under extreme conditions with dust, vibration, heat, cold, altitude, humidity, solar radiation, and fungus. You can rely on ThinkPad despite what life throws your way. Connect Anywhere, Anytime…: With 4G LTE-A, you get the fastest, most advanced mobile broadband technology. But Stay Unplugged: With the X1 Carbon, you can stay connected, yet go unplugged more than all day, as the battery lasts up to 11 hours. Battery life varies significantly with settings, usage, and other factors.