iMac with Retina 5K display

Display
27-inch (diagonal) Retina display with IPS technology; 5120‑by‑2880 resolution with support for millions of colors

Processor
3.5GHz quad-core Intel Core i5 processor (Turbo Boost up to 3.9GHz)
Configurable to 4.0GHz quad-core Intel Core i7 (Turbo Boost up to 4.4GHz).

Memory
8GB (two 4GB) of 1600MHz DDR3 memory; four SO-DIMM slots, user accessible
Configurable to 16GB or 32GB.

Storage1
1TB
1TB Fusion Drive
Configurable to 3TB Fusion Drive or 256GB, 512GB, or 1TB of flash storage (SSD).

Graphics
AMD Radeon R9 M290X graphics processor with 2GB of GDDR5 memory
Configurable to AMD Radeon R9 M295X with 4GB of GDDR5 memory.

Connections and Expansion
Headphone
SDXC card slot
USB 3
Thunderbolt 2
Gigabit Ethernet
Headphone port
SDXC card slot
Four USB 3 ports (compatible with USB 2)
Two Thunderbolt 2 ports
Mini DisplayPort output
Support for DVI, VGA, and dual-link DVI (adapters sold separately)
10/100/1000BASE-T Gigabit Ethernet (RJ-45 connector)
Kensington lock slot

Wireless
Wi-Fi
802.11ac Wi-Fi wireless networking; IEEE 802.11a/b/g/n compatible
Bluetooth
Bluetooth 4.0 wireless technology

Size and Weight
Height: 20.3 inches (51.6 cm)
Width: 25.6 inches (65.0 cm)
Stand depth: 8 inches (20.3 cm)
Weight: 21 pounds (9.54 kg)2

15‑inch with Retina display
Retina display: 15.4-inch (diagonal) LED-backlit display with IPS technology; 2880-by-1800 resolution at 220 pixels per inch with support for millions of colors
Native resolution: 2880 by 1800 pixels (Retina); scaled resolutions: 1920 by 1200, 1680 by 1050, 1280 by 800, and 1024 by 640 pixels

Processor
2.5GHz
2.5GHz quad-core Intel Core i7 processor (Turbo Boost up to 3.7GHz) with 6MB shared L3 cache
Configurable to 2.8GHz quad-core Intel Core i7 (Turbo Boost up to 4.0GHz) with 6MB shared L3 cache.

Memory
16GB of 1600MHz DDR3L onboard memory

Storage
512GB PCIe-based flash storage
Configurable to 1TB flash storage.

Sizes
Height: 0.71 inch (1.8 cm)
Width: 14.13 inches (35.89 cm)
Depth: 9.73 inches (24.71 cm)
Weight: 4.46 pounds (2.02 kg)

Graphics and Video Support
Intel Iris Pro Graphics
NVIDIA GeForce GT 750M with 2GB of GDDR5 memory and automatic graphics switching
Dual display and video mirroring: Simultaneously supports full native resolution on the built-in display and up to 2560 by 1600 pixels on up to two external displays, both at millions of colors
Thunderbolt digital video output
Native Mini DisplayPort output
DVI output using Mini DisplayPort to DVI Adapter (sold separately)
VGA output using Mini DisplayPort to VGA Adapter (sold separately)
Dual-link DVI output using Mini DisplayPort to Dual-Link DVI Adapter (sold separately)
HDMI video output
Support for 1080p resolution at up to 60Hz
Support for 3840-by-2160 resolution at 30Hz
Support for 4096-by-2160 resolution at 24Hz

Battery and Power
Up to 8 hours wireless web
Up to 8 hours iTunes movie playback
Up to 30 days standby time