It's probably a 22mm, but I don't know if the 535's ever had 22mm's installed (someone with a '92 535 want to confirm?). In order to use the 19mm, you need a metal adapter/sheath to make the 19mm shaft fit snugly in the strut mount. Alternatively, you could buy 19mm strut mounts ($120 for both?) and use them. Or, even better, you could buy the two metal sheaths that I have left over from my sachs kit install and put everything together (PM me). Best, whit