Beware of knockoffs claiming "4K support." The real Twister HD is strictly 1080p. If it says 4K, it is a different (and likely worse) chipset.
Before buying, you must understand the compromises. twister hd video mixer
Up to 8 inputs, including HD/SD-SDI, HDMI with embedded audio, CVBS (Composite), and VGA for presentation slides. Beware of knockoffs claiming "4K support