This is my first Giro ski helmet, I have used their bike helmet and loved them. Nice vent system, light, and very comfortable. My size is 23" or medium ( max 23.2"). It was too tight. So I returned it and bought a large.The large fit well with one notch to spare on the " In Form system". I would recommend that you be careful at the limits of the size range, the Medium would fit 22.75". Great color range so you can match your ski's, outfit. etc.