Timetec Hynix IC 8GB DDR4 2400MHz PC4-19200 SODIMM Memory Upgrade Compatible with Apple iMac Retina 4k/5K 21.5-inch/27-inch Mid 2017 (Single Rank 8GB) DDR4 2400MHz PC4-19200 260 Pin Unbuffered Non-ECC 1.2V CL17 Single Rank 1Rx8 based 1024x8 Power Supply: VDD=1.2V (1.14V to 1.26V) VDDQ = 1.2V (1.14V to 1.26V) Module Size: 8GB Package: 1x8GB For Apple iMac/ Mac mini/ Macbook Pro only iMac18,3 w/Retina 5K display (27-inch Mid 2017) 18,2 w/Retina 4K display (21.5-inch Mid 2017) iMac 18,1 (21.5-inch Mid 2017) Guaranteed  Lifetime warranty from Purchase Date Free technical support (support@timetecinc.com) MON - FRI 9AM-6PM PST