When placed over the front of a telescope, handy Orion PinPoint Telescope Focusing Masks make it easy to achieve quick and precise focusing without guesswork. Also known as Bahtinov masks, these focus aids feature a laser-cut slot pattern that produces a distinct, intersecting 3-line pattern once accurate focus is achieved in any type of telescope.Orion PinPoint Focusing Masks will help astrophotographers save time and avoid frustrating, fuzzy results caused by slightly defocused exposures. With a PinPoint Mask installed on an imaging telescope, just focus on any bright star within or near the celestial object you want to photograph and adjust focus until the intersecting 3-line pattern is displayed indicating precise focus has been achieved. Wow, that was fast! Besides astrophotographic applications, PinPoint Focusing Masks are also useful for visual observations when fast, tack-sharp focusing is desired.Three Orion-exclusive adjustable rubber-sleeved pegs equipped with thumbscrews clamp onto the outside of your telescope tube or dew shield to hold the PinPoint Mask firmly in place. Orion PinPoint Focusing Masks are easy to install and remove so you can achieve precise focus and quickly start capturing astrophoto exposures.Each Orion PinPoint Focusing Mask can fit a range of telescope tube diameters. For example, this 78-113mm ID Orion PinPoint Focusing Mask will fit telescope tubes with an outer diameter ranging from 78mm to 113mm (3.07 inch to 4.44 inch).Made of laser-cut black plastic. Flat for easy storage and transport.