This is a Gridfinity block that holds 9 3.5mm to 1/4" (aka 6.35mm) audio adapters in an upright position. It supports the compact style that often comes with headphones and other audio equipment (see photo).

Gridfinity specs: 1x1 footprint, 6u tall, magnet holes, stackable when not in use.

Sample printed in Elegoo PLA on a Flashforge AD5M.

OnShape source file: https://cad.onshape.com/documents/7ee6917c293eec098e48597e/w/765bd5fbefcac256a4fe404e/e/6d77dd85cc7b3c94bfbf423e

Gridfinity bin generated from: https://cad.onshape.com/documents/95d6b2cad95d26b6c62377b4/w/dffa2937aabfce2e03b5f2d2/e/47627200e70aa6e718962e14