I got a forester diesel 2012. I need to replace the front Anti Roll Bar bushes so ordered them from my Subaru dealer. The new bushes are marked 20 but when I measure my roll bar the calipers read 21mm, now is this because of the enamel coating on the bar  or are the parts wrong? I don't want to pull it to bits and then find out, because I have a some distance to go to the dealer.  

with only 1mm between part data and your measuring I would put money being they right, coming direct from dealer even more likely it right .