Sorry all, camera unavailable on the weekend so will have to wait until next week to take and upload pictures.
18cm might be a little bigger than it was now that I think about it. Can't really measure again because I took out some frustration on it - also found out how strong it was too

Also, the size of your ring will depend on how big your kite is (mine's slightly bigger than F16 at just over 18sqm) and how many retrieval holes you have. I have three which makes a fair bunch when its going in.
cheers,