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. OWC 16GB UPGRADE: Consists of a single 16GB DDR3L 1600 PC3L-12800 CL11 2Rx4 240-pin 1.35V ECC Registered DIMM Memory RAM Module Upgrade compatible with Lenovo System models x3650 M4, x3650 M4 BD, x3650 M4 HD, x3750 M4 And x3755 M3. 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 numbers 0C19535, 46W0671, 46W0672, 0C19535, 46W0671 and 46W0672.