Bilstien HD/ GC coilover question

[944Spec_bound]

I'm installing a Ground Control coilover kit and hit a roadblock. The shaft of my Bilstien struts are 24mm, the spring hats center holes are 22mm. It looks almost like there's a collar on the top part of the shaft that's making it too big. I twisted and tapped on it, doesn't budge.
Anyone know if this is supposed to come off, or if there's a 24mm ID spring hat for these struts?

Here's a pic with the spring hat upside down to show the fitment problem.



Spring hat....