4GB DDR4 PC4-21300 2666MHz 288-pin DIMM. 8GB DDR4 PC4-21300 2666MHz 288-pin DIMM. 16GB DDR4 PC4-21300 2666MHz 288-pin DIMM. 32GB DDR4 PC4-21300 2666MHz 288-pin DIMM. You can install different sized modules together in your machine.
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