Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2527418.

This is a flush fitting cable clip, designed to hook over the edge of a panel for a more secure fixing. It will suit cables of 3-4mm diameter. The slot in the clip is 4mm wide and 16mm deep, so it will fit snugly on a 4mm panel, or can be combined with double-sided foam tape. The clip is 18mm wide, stands 6.4mm proud of the panel, and is 18mm high.

This would suit any panel of 3-4mm thickness. It was originally made to secure the cable from a rear mounted Koonlung K1S Dashcam in an Abarth 500 / Fiat 500.

There's also a free standing version of this, which attaches with self-adhesive tape: https://www.thingiverse.com/thing:2236210