The Petzl Vertex Best helmet features a tough polycarbonate shell that resists impact and wear, and an adjustable chin strap to keep the helmet secure. A single adjustment wheel allows you to adjust the foam headband to two height positions. In addition, the helmet can be customized by mounting a face shield and/or standard hearing protection in the side slots. Ventilation holes can be closed with sliding shutters for cold/windy conditions. The helmet’s shell is designed with clearance over the ears to easily accommodate hearing protection that meets the ANSI Z89.1 2003 Type 1 Class E Standard.