I’ve been struggling to find the proper equipment for an extended display for my 2017 iMac for about a year now. Finally was told by Apple (after several calls to support) that the newer iMac’s don’t support Target Display Mode with other Mac’s (was trying to use my MacBook as an external display). So I broke down and bought a new monitor but I still was nervous that a simpl USB-C to HDMI cable would just make it all work... Well, it did. Connected my iMac to a Samsung monitor with this chord (which was cheaper than in any store I looked at) turned the monitor on and voila! Extended display. Picture quality is excellent, moving between both monitors is seamless. I’m happy!