The famous flip-open lens cover design with clear windows for fast target acquisition at close to medium ranges.Please refer to the SIZE CHART below for the correct cover choice for you! Lenses crafted of optical-grade polymers for optimum clarity and light transmission - the best of any see-through cover. Creates a weather-resistant seal. Ambidextrous open and close. Silent spring-loaded operation. Tested reliable in extreme conditions. For objective and ocular lenses.