Good field of vision Indirect ventilation system for improved circulation against fog Adjustable elastic headband Reinforced polycarbonate lens against impact. Letter T on the frame and lens markings for protection against Impact at extreme temperatures (-5C & +55C) Letter B on the frame and the lens markings for High energy impact resistant (120 m/s) Number 4 on the frame markings for a protection against big dust (>5 m) Number 3 on the frame markings for protection against liquid (droplets or splashes) Norms: Impact Norm - EN 166:2001