2017 21.5" inch iMac A1418 SSD Hard Drive Replacement Upgrade Screen Removal - YouTube
Upgrading an older iMac's PCIe SSD: Third-party solutions that save you beaucoup bucks | Macworld
2017 iMac SSD upgrade & Speedtest - YouTube
Timetec 256GB MAC SSD NVMe PCIe Gen3x4 3D NAND TLC Read Up to 1,950MB/s Compatible with Apple MacBook Air (2013-2015, 2017), MacBook Pro (2013-2015), iMac (2013-2019), Mac Pro (2013), Mac Mini (2014) at Amazon.com
Upgrading a 27-inch iMac 5K to 14 terabytes - Replacing the Fusion Drive with both a SSD and an harddisk