64GB (4 X 16GB) PC3-10600 240 pin DDR3 1333MHz ECC Registered 1.5v DIMM. Compatible with: Mac Pro 5,1 Mid 2010 Models; Apple Mac Pro 12-Core Mid 2010, Apple Mac Pro 4-Core Mid 2010, Apple Mac Pro 6-Core Mid 2010, Apple Mac Pro 8-Core MC561LL/A Mid 2010, Apple Mac Pro Quad-Core MC250LL/A Mid 2010, Apple Mac Pro Quad-Core MC560LL/A Mid 2010. System Specific memory backed by MemoryMasters . Additional Details ------------------------------ Package quantity: 1