This is 2 (two) 16 GB DDR2666 PC4 21300 registered ECC memory modules, for a total of 32 GB per set.

* CAS Latency: CL19
* Error Checking: ECC
* Number of Pins: 288-pin
* Buffered/Registered: Registered
* Rank: 2Rx8

* Timing: 19-19-19

* Memory Speed: 2666 MHz
* Memory Size: 16 GB
* Memory Standard: DDR4-2666/PC4-21300
* Memory Voltage: 1.20 V

Memory chips are manufactured by Hynix. (HMA82GR7AFR8N-VK)

These are used and in perfect working condition.  Tested to be flawless.  60 day free returns.