Figured it out when I removed the insert

I just finished a set of Recaros similar to those. Something else I ran into was my regular stapler couldn't get deep enough without leaving exposed staples. Grabbed a new long neck that did the job. I spent 3 different attempts perfecting those dang things but finally got something to be proud of.

I've worked on a few older Recaro seats but never completely recovered them, nice job on the black ones! Sort of like the old Volvo headrests and some others (Lexus LS) , you have to get access into the seat frame to get the clips out to remove them.