This is a clip designed to hold the headphone cable in place on the 3-in-one cable for the Vive. Doing development for VR, I usually play without headphones hooked up, so the headphone cable just dangles (and will eventually work itself out even if tucked under the wire guides) which I found to be super annoying.

This clip is designed as two pieces that fit snugly around the main cable and snap in place. The headphone jack itself fits snugly inside the opening, ensuring the headphone jack stays where you want it.