Keep a spare thinkpad 90 w ac adapter to hand to ensure your thinkpad has a consistent flow of power keep one in the office one at home and another in your carrying case for immediate convenient access to power this thinkpad ac adapter is perfect for use as a spare or replacement adapter for compatible laptops it is compatible with all lenovo laptops with the rectangular slim tip common power plug it is not compatible with legacy notebook systems with the round barrel type power plug t