Astromania flexible dew shield are constructed of black ABS plastic and are all felt lined for maximum absorption of moisture and baffling of stray light; particularly strong attachment to telescope by non-slip foam rubber at contact area to tube The flexible design is quite practical; as it allows you to slide the dew shield behind a cupboard or next to your eyepiece case; it is optimally space-saving The dew shield is lined on the inside with a black velvet-like fabric; this not only minimizes reflections but also ensures that no dew can reach the telescope's optics Height of the dew shield: 320mm; total length: 750mm; suitable for tubes from 203 mm diameter to 221 mm diameter; prevents telescope optics fogging up; keeps the optics completely dew free and lets to observe for hours with the optimal view Flexible velcro fastener provides optimal adaption to diameter of telescope or telephoto lens; place space saving around the tube; good for live in place that has dew often or use scope in the daytime and want to keep stray light out and contrast high A dew shield is an essential accessory that protects your optical tube from excess moisture forming condensation on the corrector lens. A lens shade also helps block out stray light outside the path of the telescope for better viewing and astroimaging.Astromania dew shield keeps dew away and gives you clear observing for the entire night and protect your optics from dew and stray light.In clear nights, dew is often a real problem. After only a few hours, the optics start fogging, making observations or photography impossible. A good dew shield reduces the risk of fogging and extends the observing time. On the inside, dew shields from Astromania Optics are coated with felt which absorbs dew. Dew can be a problem at almost any time of the year. Especially when it's a little cooler, tiny droplets condense out from the water vapour in the air and fog-up the optics of your telescope. The Astromania dew shield keeps dew away and gives you clear observing for the entire night. Details: Suitable for tubes: diameter from 203 mm to 221 mm Material: ABS Contact surface to the telescope: foam rubber Inner liner: black felt - light and dew absorbing Height of the dew shield: 320mm Total lenght: 750mm