rado https://ozvolvo.org/discussion/comment/188745#Comment_188745
I just measured mine at lunchtime and its 20.4 mm
Would be the same as my one then, lots of stuff on the US Volvo sites on how fun they are to install.
Grinder, blowtorch and a sharp scraper.
My original ones were in very poor shape, and this was alot cheaper then an aftermarket bar.