Fingers crossed it'll cut ally

[blackburn mark]

Just a note to say that the different size O-rings should all compress the same amount as long as they are all the of the same thickness, therein lies the problem getting the same thickness in different diameters.

sounds to good to be true, ill have to do some maths, iv got plenty of o-rings from 18mm ID to 50mm ID and they are all 3.5mm section