Kendrick dewcaps are constructed of black ABS plastic and are all felt lined for maximum absorption of moisture and baffling of stray light. The cap is attached by wrapping it around your telescope just below the corrector plate ring. The two outside ends are then attached to one another using the sewn on Velcro.
A rubber strip is supplied that must be attached along the bottom of the dewcap where there is no felt. This helps in providing a friction fit that ensures the dewcap stays in place once attached. It also allows enough room to attach Kendrick heaters around the corrector plate ring on the inside of the dewcap.
Dewcaps will not prevent dew from forming on your telescope. They only delay it, typically by 20 to 40 minutes after dew point has been reached. A dewcap will provide greater contrast while observing by cutting down on the amount of stray light that enters the front of your telescope due to street lights, skyglow etc.