4K displays have become more and more popular in the last year and 2017 should be the biggest year yet for 4K.
The latest MacBook and the previous years (2016 and 2015) also support 4K, depending on which model you get.
We've made a guide for you on various 4K displays you should consider for your MacBook Pro.
Note: You will get 4K at 60hz on ALL of these displays if you connect them via DisplayPort. Do not use HDMI.
The Dell P2715Q is one I stand by. I have one myself and use it alongside my MacBook Pro everyday. It's a fantastic monitor for those who want to get the color as close as possible to the MacBook display. It's very easy to setup and comes with a DisplayPort to Mini DisplayPort cable that goes directly into the 2015 MacBook Pro without any additional dongles. You will need a dongle for the 2016 model. It works at 60hz at 4K perfectly. The monitor also has a lot flexibility, letting you adjust height, tilt and you can even rotate the display.
ASUS are well known in the display game and were one of the recommended partners by Apple themselves when it came to a 4K display for the MacBook Pro. It's 28 inches in size and offers the usual array of ports including displayport and HDMI. This monitor will also let you adjust height, title and let you rotate the display.
The LG is very similar to the other displays above. There isn't actually much separating them other than the design. However the LG does fall short in the adjustability department because it doesn't let you rotate the display. Not much of an issue for most.
The Samsung display is very similar to the LG above in terms of design and adjustability. It is a fantastic display nonetheless and features two HDMI ports and a single DisplayPort.
If you're looking to splash some cash and want seamless integration with the brand new 2016 MacBook Pro, the UltraFine is a good choice. However for the price you really are paying a premium and it's only 21.5 inches in size - smaller than all of the displays above.