Troy lee designs d2 helmet fusion blackthis benchmark d2 fusion helmet from troy lee designs is a full face helmet with legendary tld styling and the top choice bicycle helmet for more championship winning riders than any other helmet in its class this incredibly lightweight and markedly strong d2 helmet is ideal for bmxing mountain biking and other sports such as snowboarding optimum ventilationthe d2 is constructed from an aerospace composite shell with a high flow ventilation system incor