Lenmar Portable Power Pack for Laptops and Notebooks is a 16500mAh Lithium-Polymer battery externally powers your laptop while charging the internal battery providing several hours of extra productivity; Includes a USB output port for charging cell phones mp3 players and other USB powered devices; Compact lightweight and ultra-thin - fits easily into your laptop case backpack or briefcase for travel; Fully recharges in 3-4 hours using your laptop's AC power adapter and included adapter tips.