IBM IntelliStation Z Pro computers are older systems that use DDR SDRAM memory modules. Memory America has a large selection of SDRAM modules for these computers that are brand new and are qualified to work in these systems. There are more than 50 models of IntelliStation Z Pro computers so you should either consult with your user manual or pull an existing module from the computer to make sure you order the correct replacement memory stick. As an example, the Type 6221 version of this computer uses DDR PC2100 RAM. As you upgrade RAM modules, be sure to use new DIMMs to achieve the best possible speeds, as opposed to populating the system with a combination of old and new memory modules.