ib. Raws li qhov loj ntawm lub pob (piv txwv li, qhov loj ntawm txoj kab uas hla)
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. Muaj lwm txoj hauv kev qhia qhov loj ntawm lub pob, uas yog L
