[shyun]

Originally Posted by Citroënbender

Since the question comes up often and I am yet to see a concise answer that doesn’t involve Ford part numbers:

Tensioner assembly o-ring sizes for the AU, numbered per BS1806, a parallel industry standard. I suggest buying them in Viton or HNBR, not regular NBR.

013 filter basket, buy two
017 retainer nose, buy one
109 plug midlength seal, buy one
118 tensioner flange, buy one

Came across this and measured my o-rings since they are mostly stuffed and leaking too. They all seem correct except the 'Tensioner flange' (Ford P/N V 890066 S) should be BS 210 (ID: 18.64 S: 3.53 OD: 25.70)