OWC DIY Drive Upgrade/Install Kits for Apple iMac Models
iMac Late 2012 21.5 inch A1418 - Disassembly SSD Upgrade, 10.8 Snow Leopard to 10.15 Catalina macOS - YouTube
Should I Upgrade My Mac to SSD? - Best Mac Optimization Software Reviews
SSD Upgrade Kits For 21.5 Inch iMac 2012 - 2013
OWCDIDIM27SSD10, OWC Internal SSD DIY Kit, For All Apple 27" iMac 2010 Models, iMac to SSD SATA 3Gb/s data cable, iMac to SSD/HDD power "Y" cable, Thermal safe adhesive mounting set