I recently bought a 50mm ring & a 55mm, the 50mm I tried first as I was always having chaffing issues with the 45mm ring which I bought elsewhere, luckily the cage I had fitted the 50mm ring just a slight adjustment. My issue is why can't I buy a new cage with a 50mm ring, by default all cages come with 45mm ring,therefore if I want a different cage I'm going to end up with a few 45mm rings I don't need.