HyperX 7.1 Surround Sound USB Audio Control Card

The in-line box that turns a plain 3.5 mm headset into a virtual 7.1 one, with the volume and the microphone mute moved off the cable and onto something you can find without looking.

It is the part HyperX ships with some Cloud headsets and sells separately for the rest, so it upgrades a headset you already own rather than replacing it. Twenty in stock at twenty dollars.