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A-Tech for Apple 1GB DDR2 667MHz PC2-5300 200-pin SODIMM for MacBook, MacBook Pro, iMac, Mac Mini - (Early/Mid/Late 2006, Mid/Late 2007, Early 2008, Early 2009) - Memory RAM Module at Amazon.com
Mid 2011 Apple iMac 21.5" A1311 i5 2.7GHz 8GB RAM 1TB HD OSX Sierra - DCPS Computer Program
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET