All IBM RackSwitch products ship with 2-post rack mount kits. IBM offers three different 4-post rail mount kit options depending on what type of deployments you are considering, the first one is the most commonly used with its ability to fit a variety of racks 27” to 32” apart.
System x PN
Storage & Power FC
IBM System Networking Adjustable 19" 4 Post Rail Kit
IBM iDataPlex Rail Kit
IBM System Networking Recessed 19" 4 Post Rail Kit (ideal for NeXtScale)
* Feature codes specific to Power & Storage ordering system