In addition to using a display, TV or projector that can support that spec, you'll also need to be playing videos from a 15-inch MacBook Pro introduced in 2017 or later, a Retina iMac introduced in 2017 or later, an iMac Pro or an iPad Pro. Further, your devices must be running macOS Mojave 10.14.6 or later or iOS 12.4 or later. The upgraded accessory also adds support for HDR10 and Dolby Vision, two competing HDR formats becoming more common today.

Apple has already discontinued the adapter's older version, which only supports HDMI 1.4b, so you're getting the updated model when you buy from its online store. If you're buying elsewhere or want to be sure, though, the new version is Model A2119, while the older one is Model A1621.