They are the same but different model
They both have different MHz but their Latency is very similar
Also the Voltage is different
http://www.gskill.com/en/product/f3-1866c9d-8gab
http://www.gskill.com/en/product/f3-2133c9d-8gab#tabs-spec
They both have different MHz but their Latency is very similar
Also the Voltage is different
http://www.gskill.com/en/product/f3-1866c9d-8gab
http://www.gskill.com/en/product/f3-2133c9d-8gab#tabs-spec