The 17mm plug is part # 807016210 based upon info in another thread. When I asked my Subaru parts counter if that was the correct replacement for the 14mm plug, he said yes. I haven't switched it out yet with the 14mm plug but will do so on my next oil change.
Question. Label on the packaging says it is "16x17". 17mm apparently is the head size but what does 16 refer to? The thread diameter?
I was at my local dealership this morning. The looked up the crush washer and plug using my VIN. The washer fit the plug perfectly. I bought the washer for under $2 (just in case) and when I got it home it measured 16mm. I'm going to order the Fumoto 108 series, which is for M16-1.5 plugs.
I just did my oil change and replaced the factory Oil Drain plug with a 16x17 Part#: 807016210 (16mm thread / 17mm Head) and it fit perfectly. The one that comes with the '18 Forester Touring was a 14mm head and it was starting to get rounded. So glad I ordered the larger size nut! Attached is the part for an '18 Forester Touring. The larger nut size is a little longer than the 14inch but no issues. (And yes, I posted this response in another thread but just trying to help here as well.)