The R4 is a lightweight, form-fitting race collar offering protection against neck and collarbone injuries. The low profile design makes it a comfortable yet protective piece of gear you can wear on the track or on the trail. Hard molded upper surface disperses energy to polyurethane core. High-tensile closed cell polyurethane core absorbs impact energy. Bio-foam liner provides extra impact absorption. Rapid lock closure system for easy front entry. Adjustable rear strut for a customized fit. Weight: 635 grams. Adult size is generally for riders over 5'3" (152 cm) or 106 pounds (48 kg).