How to Upgrade/Replace the PCIe SSD in a 21.5-inch iMac (Late 2013) on Vimeo
Apple iMac 21.5” SSD Upgrade (2013-2015) HDD To Solid State Drive (SATA) | Step By Step - YouTube
SSD Upgrade Kits for 27-Inch iMac (2012 - Early 2013)
Amazon.com: Sintech M.2 nVME SSD Adapter Card Upgrade Kits,Compatible for MacBook Air(2013-2017 Year) and MacBook PRO(Late 2013-2015 Year,iMac : Electronics
Amazon.com: PCIe NVMe Gen3x4 SSD 1TB 512GB 256GB 128GB 3D TLC NAND Flash Hard Drive SSD Replacement for Macbook Air 2013-2017, Macbook Pro Retina 2013-2015, iMac 2013-2017, Mac Pro 2013, Mac Mini 2014 (1TB) : Electronics
OWC Aura SSD Install: 21.5-inch iMac Late 2012 – Early 2013 - YouTube
How to Install/Upgrade the PCIe SSD in a 27-inch iMac (Late 2013) iMac14,2 - YouTube