21.5-inch  

21.5-inch with Retina display

27-inch with Retina display

Display1
21.5-inch display21.5-inch display Retina 4k display27-inch Retina 5k display
1920*1080 resolution4096*2304 resolution5120*2880 resolution
Processor
Dual-core or quad-core Intel Core i5Quad-core Intel Core i5Quad-core Intel Core i5
Memory
8GB8GB8GB
Strorage2
1TB hard drive1TB hard drive1TB hard drive or
1TB or 2TB Fusion Drive
Intel HD Graphics 6000 orIntel Iris Pro Graphics 6200AMD Radeon R9 M380, M390 or
Intel Iris Pro Graphics 6200M395 with 2GB GDDR5
Wireless
802.11ac Wi-Fi802.11ac Wi-Fi802.11ac Wi-Fi
Bluetooth 4.0Bluetooth 4.0Bluetooth 4.0
Connections and Expansion
Two Thunderbolt 2 portsTwo Thunderbolt 2 portsTwo Thunderbolt 2 ports
Four USB 3 portsFour USB 3 portsFour USB 3 ports
SDXC card slotSDXC card slotSDXC card slot
Camera
FaceTime HD CameraFaceTime HD CameraFaceTime HD Camera
Keyboard and Mouse
Magic KeyboardMagic KeyboardMagic Keyboard
Magic Mouse 2Magic Mouse 2Magic Mouse 2