Transcend 4GB (2GB x 2 Kit) DDR2- 800 Fully Buffered DIMM 2Rx8 For Mac Pro 2006/2007/2008 (TS4GJMA251U) For iMac 27" (Mid 2011-Late 2012), MacBook Pro (Early 2011-Mid 2012), and Mac mini (Mid 2011-Late 2012) 512Mx8 bit 1.5V Timing 11-11-11 Operating Temperature 0 ~ 85 C Compatible with select Mac systems. Verify model for compatibility Fully Buffered DIMM 128Mx8 bit 800 Mbps 1.8V Timing 6-6-6 2 Ranks Operating Temp. 0 DegreeC ~ 85 DegreeC Compatible with selected Mac systems. Verify model for compatibility