The Chrono Expert Wind Undershirt is made from lightweight and windproof 2-way stretch ripstop creating a protective barrier against the bite of cold winds, whether that's an early morning start or a descent from a mountain pass. A Durable Water Repellent finish also keeps light rain and quick rain showers at bay. To ensure you don't overheat or get too sweaty Giro gives the gilet a perforated back panel to enhance ventilation and moisture management. The sleek, form-fitting cut keeps flapping to a minimum while genuine 3M Reflective logos and highlights add visual pop in low light conditions.