OWC 48.0GB UPGRADE: Consists of a Six 8GB DDR3 1333MHz PC3-10600 CL9 ECC DIMMs 1.5V 240-pin Memory Module with Mac qualified Thermal Sensor EEPROM 100% COMPLIANT: With JEDEC Standard Specifications, ROHS Compliant, Warranty Safe Upgrade. Designed and Tested to Meet or Exceed All MAC Specifications for Mac Pro 2009-2012 Nehalem & Westmere 4,1 and 5,1 COMPATIBLE PART NUMBERS: KTA-MP1333/8G, KTA-MP1333S/8G, KTA-MP1066/8G, KTA-MP1066S/8G, HMT31GR7AFR4C-H9, M391B1G73BH0-CH9, M391B1G73AH0-CH9 COMPATIBLE WITH: Mac Pro 12-Core (Model ID: MacPro5,1) Mac Pro 8-Core (Model ID: MacPro5,1) Mac Pro 8-Core (Model ID: MacPro4,1) Mac Pro 12-Core Mid 2010-2012, July, 2010/ June 2012, MacPro5,1 2.4GHz, 2.66GHz, 3.06GHz INDUSTRY LEADING: Consumer Friendly Advanced Replacement Program and Limited Lifetime Warranty, which Includes Free Tech Support by Other World Computing