RAM & Memory Upgrades
16GB DDR4 2400MHz PC4-19200 260-PIN SODIMM MEMORY RAM COMPATIBLE WITH INTEL 27" RETINA 5K IMAC (2017)
SIZE/CAPACITY: 16GB VOLTAGE/POWER CONSUMPTION: 1.2v CAS LATENCY: CL17 SPEED: PC4-19200 (2400MHz) TYPE/INTERFACE: 260-PIN DDR4 SODIMM 260-PIN INTEL IMAC DDR4 SODIMM
https://www.bizrate.co.uk/ram_memoryupgrades/16gb-ddr4-2400mhz-pc4-19200-260-pin-oid7773820421.html