Size S: adjustable head size, from 51 to 54 cm (using a toothed wheel), removable comfort foams, 11 ventilation holes, 3 adjustment points. Inner shell (EPS), outer shell (PC, polycarbonate) – Foams : Polyurethane (PU) – Straps : Polyester (PE). Sold on a pegbordable hangtag.Adjustable head perimeter (47 to 54cm)Removable comfort foams11 Ventilation Holes3 Ways to Adjust Size25x20x15.5cm « less