OWC 16GB (4 x 4GB) PC8500 DDR3 1066MHz SO-DIMMs Memory Compatible With iMac 21.5" and 27" (October/2009) Product Specs: Technology: DDR3 SDRAM Density: 4GB (4096MB) RoHS: Yes Pin Count: 204-pin Op. Temp.: 0C to +85C Data Rate: DDR3-1066 Speed: PC3-8500 CL: CL = 7 Cycle Time: 1.875ns Voltage: 1.5V ECC: Non ECC Module Ranks: Dual Rank Register: Non Parity Low Noise 8-Layer PCB Meets and/or Exceeds Specifications Fully compliant with JEDEC specifications Individually OWC MaxRAM Memory Certified for 6GB MacBook/MacBook Pro compatibility Lifetime OWC Limited Warranty