Tech Rover Replacement Battery for Sony Vaio VGN-CR420E/L [No BIOS Update Required] trade; Max-Life Series 6-Cell [Silver] [Plug-and-Play] Plug-and-Play, No BIOS update or system changes required. Works with all Windows Operating Systems. Tech Rover&trade; Quality product with 30-DAY Worry-Free Return Policy Brand New Battery, 4400-5200 mAh, Effective Capacity All Tech Rover&trade; branded items carry a 1 year warranty against manufacturer defects. 6-Cell [Standard-Capacity] Battery, 100% Compatible