Center pin diameter: 2.5mm IBM Thinkpad:T40, T41, T42, T43, T44, T45, R50, R51, R52, R53, R54 IBM ThinkPad DC Power Jack Connector: T40, T41, T42, T43, R50, R51, R52 IBM T40 T41 IBM ThinkPad T40 T41 T42 T43 T40p T41p T42p R50 R50e R50p R51 R51e R51p R52 R52e R52p