990 superduke disc bolts

are the disc bolts any particular size or are they just a standard bolt ,I want to put some titanium or stainless ones on in place of the rusty ones on at the moment but can not see them listed , lots on for other Ktm models ,any body know what will fit. ,thanks

61009062018 SPECIAL SCREW M8X18

Why do Ktm do them in a 18 length when everbody that does stainless or titanium has them in 16 or 20 mm off the shelf, looks like silver paint could be out , or will have to get them in 20 and get a engineering firm to take a bit off , nothing is ever easy ,