Can you upgrade the RAM in the 27-inch iMac? | iMore
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Apple iMac 2015 (mid) 21.5-inch SSD & macOS X Upgrades - ZD Laptop Service Centre
Install memory in an iMac - Apple Support
Apple iMac (21.5-inch, Late 2015) review | TechRadar
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac
Install memory in an iMac - Apple Support
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com