This IBM ThinkPad R51 Series 54WHr Portable Power Pack is 100% compatable with the PBASE-JR-IBM IBM ThinkPad R51 Series 54WHr Portable Power Pack. Our batteries and accessories are made with high quality parts and are guaranteed to meet or exceed the original equipment manufacturers specifications at a reduced price. All batteries are tested for 100% quality control assurance. This IBM ThinkPad R51 Series 54WHr Portable Power Pack includes a warranty to guarantee that it has no manufacturing defects.