There are 3 models : S ( accurately measures from 42~52 cm,it fits kids' hats) , It has just one scales and will read in CM measure. M (accurately measures from 6 1/8 US to 7 3/4 US,it fits most adults' hats),It has four scales and will read in US, UK, CM and French measure. L(accurately measures from 55~68 cm,it fits extra large adults' hats).It has just one scales and will read in CM measure. This is a Chinese made tool,is made of Cu(copper). It is hard to find.