The Blackmagic Design Mini Converter SDI To HDMI 4K will let you output 4K video from an SDI device to a 4K HDMI display, such as a 4K projector or 4K TV, over a single HDMI cable, with an included software there to help you do so efficiently.
The converter has 4 SDI inputs and 1 HDMI output. You get two conversion methods to choose from -- Quad Link or Dual Link. You can either connect four SDI cables from an SDI device, like from a Blackmagic Design DeckLink Extreme 4K, and transfer a 4K signal at 1.5 Gb/s, transferring one of four quadrants of a 4K signal through each cable, or you can connect two SDI cables and transfer at 3 Gb/s. Both ways will send the full 4K signal through the converter and out by one HDMI cable, letting you monitor the signal on a 4K HDMI display.
All the connectors, SDI and HDMI, are of the highest quality, with the SDI inputs featuring low jitter processing and cable length reclocking that would let you use the longest SDI cables available without losing on image quality. The Converter also has a tie down loop to tightly secure cables to.