i know this is a bit random but i want to get some wheel spacers made specific to my oettinger re wheels in 19x8.5. therefore I'm hoping some kind sole can inform me of the diameter of the back face of the wheel that mates with the car hub / brake disc. i hope that makes sense, see below photo of dimension highlighted in red if that helps...

why don't i just measure my own wheel i hear you ask... i won't be back to my car for 3 weeks and i would like to get the spacers ordered in time to collect when i get home. its the only bloody dimension if i forgot to take before i left...

thanks in advance if anyone can help please...