Measure before printing!

The headrest hook is designed for seat headrest with bars exactly 17cm apart (measured from bar center).

The STEP file is uploaded here if you want to modify it.

Preferably print with tougher material that can withstand higher temperature (e.g PETG), particularly in hot climate (in a car, no less).

Printing: To avoid wastage on supporting section, enable support, and set "Support Overhang Angle" to 88 degree (with cura setup), the preview should look like the attached screenshot below.