Used Apple iMac 21.5-inch (Retina 4K) 3.6GHZ Quad Core i7 (Mid 2017) MNE02LL/A-BTO - GainSaver
Restored Apple iMac 21.5" Thin Desktop Computer Intel Core i5 2.7GHz 8GB RAM 1TB HD Mac OS Sierra MD093LL/A with USB Keyboard and Bluetooth Mouse- (Refurbished) - Walmart.com
Apple iMac review (21.5-inch, 2015): 4K is optional, faster hard drives shouldn't be | Engadget
Apple iMac 2.5Ghz i5 21.5-Inch (Mid-2011) *Scratched Glass* #1 – MSU Surplus Store