Yes, your 4K cable box handshakes with converter/splitter and discovers that these are 1080p only capable, hence you won't go beyond that 1080p which is what you are getting. Even if Slingbox had 4K box, your converter/HDMI splitter would have to be 4K capable... and... both your TV and Slingbox would have to work in 4K mode. Aside of the fact pushing 4K through streamers does not make much sense unless used in some Gigabit LAN, I am not sure what would be the purpose of this exercise as bandwidth required to stream in true 4K (not to me mistaken by crappy Netflix/DirectTV semi-4K quality which by the way meets 4K resolution but uses compression that reduces details to 1080p or less) would have to be above 15-20Mbps. With such link use, you would quickly discover that your internet provider caps you fast. I do not mean disrespect but my suggestion is to get back to earth and stream 720p or 1080p which gives great results for remote connections with minimum uplink capacity of 5Mbps or more. But if you want to enjoy 4K on your TV while streaming supported 1080p, you most likely have to obtain: 4K capable splitter (which may be expensive) plus 4K capable HDMI to Component converter (which also may be expensive). My experience reaches HDFury2 which works with 1080p, sorry I never shopped for 4K version and 4K capable splitters. Good luck!