I’d say it’s roughly about 12mm but squashes to around 5mm when it sits against the roof.Do you know the profile of the golf door shut seal? Did you buy precut PPF
I got some off cut pieces of PPF from a local company that fit full kits. I initially approached them to fit something for me but with it being such a small easy area he just gave me a few bit to do it myself. As long as you have a squeegee it’s dead easy to apply as it’s all flat areas.