a. De réir mhéid an chnaipe (ie, méid an trastomhas)
That is, we often say 14, 16, 18, 20, 60 and so on! Its conversion formula is: diameter = model 0.635 (mm). If we have a button in our hand, but don't know its size, we can use a caliper to measure its diameter (mm) and divide it by 0.635.
b. Tá bealach eile ann chun méid an chnaipe a chur in iúl, eadhon L
