This listing is for a set of two 4Gb DIMMs. I have two sets available for a max of four DIMMs.

Technical Specifications for HMA451R7MFR8N-TF

Manufacturer                    Hynix
Manufacturer Part #       HMA451R7MFR8N-TF
Memory Type                    DDR4 SDRAM
Capacity                               4GB
Data Transfer Rate           2133Mhz
Pins                                        288 Pin
Bus Type                              PC-17000
Error Correction                Registered ECC
Cycle Time                          0.93ns
Cas                                         CL15
Memory Clock                   266Mhz
Rank                                      1
Voltage                                 1.2