OWC 16GB DDR4 3200MHz PC4-25600 CL22 1.2V 288pin Server DIMM ECC Registered memory compatible with Lenovo ThinkSystem models SR635, SR655, SR850 (Xeon SP Gen 2) and SR860 (Xeon SP Gen 2). ECC REGISTERED UPGRADE: This type of memory is used in Workstations and Servers. It will NOT be compatible with standard desktop computers. Also, it cannot be mixed with UNBUFFERED memory. INDUSTRY LEADING: Consumer-friendly Advanced Replacement Program and Limited Lifetime Warranty, which includes Free Tech Support by Other World Computing. MAXIMIZE YOUR SERVER: With OWC's ECC Registered Server Memory, you will extend the life of your old infrastructure or save money when building a new one. Replacement for Lenovo part number 4ZC7A15121.