Just received my 2nd one of these. Have put them on the end of a 25m HDMI run from a 4K Apple TV and also a 4K Blu-ray player. Had repeaters previously but they were not 4K compliant so no picture on my LG 4K UHD TV.
These work great but need power via a mini USB to USB cable and a USB power plug. Absolutely plug and play. The switch on the repeater for short or long length is also a bonus.
Have bought a few items from Space HiFi over the past 2 years. Prompt delivery, helpful advice over the phone and quality products!