I'm selling a used HP ENVY 27-inch 4K monitor (same as this product: https://www.amazon.com/HP-27-inch-Monitor-Micro-edge-FreeSync/dp/B01N3YVA0P) that is in great condition. I bought the monitor on Craigslist a few months ago to use with my MacBook Pro (2016) via USB-C and the monitor worked for a while I can no longer get the monitor to detect the computer. Apparently the monitor is known to have difficulties with Macs (https://9to5mac.com/2017/02/06/affordable-macbook-pro-display-hp-envy-4k-usb-c/).

The monitor comes with its box and the orignal cables (USB Type-C, HDMI, DisplayPort).

The monitor is great but should not be used with Macs. $300 is a great price for a 4K monitor. Once you use a higher DPI, you won't want to go back!

Given that I've had difficulties with the monitor, you can return it to me (full money back) if it doesn't work for you.