OWC 32.0GB UPGRADE: Consists of Four 8GB DDR3 1066MHz PC3-8500 CL7 SO-DIMMs 1.5V 204-pin Memory Module Compatible with Mac and PC 100% COMPLIANT: With JEDEC Standard Specifications, ROHS Compliant, Warranty Safe Upgrade. Designed and Tested to Meet or Exceed All MAC Specifications for iMac and PC Laptops COMPATIBLE WITH: iMac 27-inch (Late 2009 Model ID: iMac11,1) COMPATIBLE PART NUMBERS: CT8G3S1339M, M471B1G73CB0-YF8, M471B1G73CB0-CF8, HMT41GS6BFR8C-G7 INCREASED PERFORMANCE: Memory Upgrades are the Most Effective and Easy Way to Boost the Performance in Your Mac or PC INDUSTRY LEADING: Consumer Friendly Advanced Replacement Program and Limited Lifetime Warranty, which Includes Free Tech Support by Other World Computing