Timetec 8GB Compatible for Apple 2017 iMac (27-inch w/Retina 5K, 21.5-inch w/Retina 4K / Non-Retina 4K) DDR4 2400MHz PC4-19200 CL17 SODIMM Memory MAC RAM Upgrade for iMac 18,1 / iMac 18,2 /
Adamanta 16GB (2x8GB) Memory Upgrade Compatible for 2017 Apple iMac 27"/21.5" Retina 5K/4K or Non-Retina Display DDR4 2400MHz PC4-19200 SODIMM 1Rx8 CL17 1.2v Single Rank RAM DRAM at Amazon.com