This is a great helmet. Fits perfectly with my fairly small head and is real comfortable. Also keeps your head nice and warm so no need for wearing a hat underneath. I would recommend this to anyone looking for a non-expensive but protective helmet. Here's the sizing so you do not have to go looking:
XS(52-54 cm), S(54-56 cm), M(56-58 cm), L(58-60 cm), XL(60-62 cm). The measurements are pretty much right on the money. My head measured from 52-54 cm and the size fit perfect. Just measure your head all the way around and purchase the size that fits your measurement-range.