Key Features:A specially developed mask to provide country and sports cyclists with excellent protection against particulate pollution,Uses a HEPA-type filter to protect against sub-micron particulates such as pollens and respirable dust,Includes two free-flowing Powa valves to allow unimpeded exhalation, which is particularly important when riding at your limit,Comes in two sizes, with a contoured shape for a snug and comfortable fit, and Velcro pads for easy application,Made from aerated Neotex giving a lightweight and well-vented mask,The filter is replaceable and is designed to remain effective until a noticeable discolouration of the filter occurs.