Used iMac 21.5-inch Retina 4K 3.4GHz Quad-Core i5/8GB RAM/1TB Fusion Drive (2017)

Powerful graphics, fast processor, Thunderbolt 3, fast storage and the stunning  Retina 4K display

21.5-inch (diagonal) Retina 4K display
4096-by-2304 resolution with support for one billion colours
3.4GHz quad‑core Intel Core i5 (Turbo Boost up to 3.8GHz)
8GB of 2133MHz DDR4 memory
1TB Fusion Disk Drive
Radeon Pro 560 with 4GB of VRAM

Full Specifications