A:Answer YES! This coupler supports 4K & ARC. That is precisely my use:
AudioQuest is well known as the manufacturer of the very BEST high end HDMI, Audio & Video Cables on the market. So it was my brand of choice when I needed to extend an HDMI cable in my drum studio. The existing 25' HDMI cable was hardwired in a drywall wall / ceiling & trying to pull it out & replace it with a longer run would have created a mess.
I ordered this coupler from Best Buy, plugged it in to the existing 25 foot HDMI cable & added a 10 foot HDMI cable to reach the Blu-Ray player.
Please see photos that show the coupler & both ends of 2) HDMI cables that it connects.
I will neaten up the installation with a wall cover plate, but wanted to show a clear view of the simple installation first.
I highly recommend this AudioQuest HDMI coupler. I can see no loss in the picture quality whatsoever on my new 70" LG TV.