Fit is accomplished with interior padding and the suspension system. Padding is either polyethylene or closed-cell foam. Poly-based foams are used in plastic helmets. Shell sizing, or a universal shell size with a variety of liner thicknesses, accomplishes the task of fitting different head shapes. Part of the fun of a composite helmet, however, is customizing the liner to fit your head like a glove.
Suspension systems vary as much as helmet styles.
The most effective systems are four-point with polypro webbing. These are generally four-way adjustable with a Fastex buckle and offer the best fit and adjustment. Less adequate suspension systems feature everything from two-point adjustability with webbing and buckles to plastic straps and snap buckles. Look for stainless steel hardware. You should also be able to adjust your helmet with cold hands, and make sure the straps do not irritate your chin or eyewear.