2 x 8GB 2400MHZ DDR4 SO-DIMM PC4-19200 OWC Memory Lifetime Limited Warranty including the OWC Lifetime Advanced Replacement Program | 30 Day Money Back Guarantee iMac w/Retina 5K display (27-inch Mid 2017) (June 2017) Model ID: iMac18,3 3.4GHz i5, 3.5GHz i5, 3.8GHz i5, 4.2GHz i7
https://eshop.macsales.com/item/OWC/2400DDR4S16P/
We do not accept memory returns