it doesn't list 3480 X 2160 as an input which is the resolution of 4k so why does it say 4K ? I need to go from a 4k stream box provided by my cable company

The product supports HDMI input resolutions up to 4K@30Hz. This includes 4K resolution as an input format.

Questions & Answers: 4K HDMI To AV HDMI Converter 1080P 60hz HDMI To CVBS RCA Composite Video 2 In 1 HD Splitter for PS Monitor TV Projector Camera

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4K HDMI To AV HDMI Converter 1080P 60hz HDMI To CVBS RCA Composite Video 2 In 1 HD Splitter for PS Monitor TV Projector Camera

One Input To Two Output
This HDMI to RCA hdmi to hdmi Adapter,Video Converters and HDMI Adapter Converter,hdmi to rca coverter, can distribute 1 HDMI input signal to HDMI Output + CVBS composite video signal and L/R stereo audio Output , transmit video and audio simultaneously, no loss, no lag .(Come with a 5V1A Power adapter).
FEATURES:
1.Hardware Conversion,Plug and Play without any software driver.
2.Compatible:HDMI 1.3 .
3.Output the audio synchronization with video.(One HDMI input,one AV output,one Stereo output.
4.High bandwidth capability support 1080P@60Hz.
5.Support NTSC and PAL two standard TV formats output.
HDMI Input Format- Support 480P/576P/720P/1080p@60hz simultaneously compatible with DVI mode: 800x600/1024x768 / 1280x720/1280x1024/1920x1080/60hz; AV video output: 480i/576i (optional) ; Audio output: L/R channels ; Support the HDCP Protocol,support for HDMI 1.3. Support play on TV,Compatible with VHS VCR,XBOX360,PS3,Set-top boxes, DVD recorders, etc.