hardware - Can I add different size RAMs to iMac 5K? - Ask Different
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NEMIX RAM 16GB Memory Upgrade Kit (2x8GB) DDR3L 1600MHz PC3L-12800 SODIMM Compatible for Apple for Mac Book Pro(Early/Mid 2012), iMac, Mac Min at Amazon.com
Install memory in an iMac - Apple Support
iMac 27-Inch "Core i5" 3.5 (5K, Late 2014) Specs (Retina 5K, Late 2014, MF886LL/A, iMac15,1, A1419, 2806): EveryMac.com
The New 2017 iMac: Notes & Tidbits on RAM - The Mac Observer
iMac Repair & Upgrade, Same Day Services
Apple iMac with 5K Retina display (27-inch) review: Apple's 5K iMac impresses expert eyes (review) - CNET
How to Upgrade iMac Hard Drive or SSD 2012-2022: EveryMac.com