To properly install the grommets you will likely need to remove the headrest covers. Then you can measure the alignment with the location for recessed bolt head that allows you to adjust tension for the headrest tilt. I only mention this because some people reading this may not know what these grommets are for since I believe they were not present on all models.
Also, these grommets are not available separately. In my case, they can be very brittle, especially the retainer ring on the back side so extra caution is needed when handling these. Buds offers a machined aluminum grommet.
