hard drive - iMac 27" late 2012 SSD upgrade - Ask Different
2013 iMac teardowns reveal SSD slots, soldered-in CPU in the 21.5” model | Ars Technica
maxupgrades.com: Dual SSD Drives kit for iMac 27 inch 2012 Models with Blade SSD Module with Heatsink and Power and DATA Cables
Original 128GB PCI-e SSD Replacement for MacBook Pro Late 2013 - Mid 2014, MacBook Air Mid 2013 - Early 2014, iMac Late 2013 - Mid 2015, Mac Mini Late 2014 (Bulk, No Retail Packaging) : Electronics
Apple iMac 21.5” SSD Upgrade (2013-2015) HDD To Solid State Drive (SATA) | Step By Step - YouTube
Original 512GB SSD MZ-JPU512T/0A6 For Apple iMac 21.5-inch A1418 Retina(Late 2013 – Late 2015), iMac 27-inch A1419 Retina(Late 2013 – Late 2015), Mac mini (Late 2014), Mac Pro (Late 2013), MacBook Air