If any of your splitter outputs need to be extended to other locations (e.g. bedrooms) more than 15m (recommended max. length of an HDMI cable) you will need to use HDMI Extenders.
Extenders are paired devices been a sender unit (located at your HDMI source and connected to one of the splitter outputs) and a receiver unit located at the extended TV e.g. bedroom. Extenders are connected to each other via CAT6 cable and are available in 30m, 60m and 120m ranges been the length of the CAT cable itself and not the distance to the extended location e.g. bedroom.
NOTE: It is possible to have a combination of 60m and 120m HDMI Extenders connected to any of the splitter.