Full Details from Amazon.com : http://www.amazon.com/gp/product/B00JIJU9SW?tag=onigi-20Transcend 32 GB DDR3-1333 ECC Registered DIMM 2Rx4 TS32GJMA533Y (8GB x 4 |Mac Pro Early 2009Registered DIMM 512Mx4 bit 1333 Mbps 15V Timing 9-9-9 2 Ranks