The Focusing Mask Lens Cap and Long 105mm Dew Shield are high-quality accessories for astronomers and astrophotographers. It is made of durable and lightweight PLA MATTE material that provides reflective reduced properties, which will reduce stray light reflections. This accessory is compatible with ZWO Seestar s50 Smart Telescope and is also Universal for other brands.The ZWO Seestar s50 Smart Telescope Focusing Mask Lens Cap Long Dew Shield have great features such as Stray Light Reduction, Bahtinov Focusing Mask, and Dust Protection. It is an excellent tool for astrophotography as it reduces stray light reflections and provides protection against dust while telescope not in use.