The bahtinov mask makes focusing on astrophotography an easy task. Manufactured with professional technology, the aluminum alloy material ensures the durability of the product. It takes less time to achieve perfect focus with the new mask, which means you will spend more time observing celestial objects. Features - Material: Aluminum alloy - Color: Black - Diameter: 9.50 x 9.50 x 0.10 cm / 3.74 x 3.74 x 0.04 inches - Note: Suitable for telescopes with an outer diameter of about 63-89 mm / 2.4-3.5 inches - Professional technology: Manufactured with professional technology, the aluminum alloy material ensures the durability of the product. - Easy focus: The bahtinov focus mask makes focusing in astrophotography quick and easy. - Works well: It takes less time to achieve perfect focus with the new mask, which means you'll spend more time . - Easy to install: Gently but firmly clamp the telescope tube with three metal posts, which have a scratch-resistant silicon sleeve to protect the telescope surface. - Universal design: Suitable for all types of telescopes, allowing you to quickly observe images of bright stars after focusing. Please pay attention to the size before purchase. Package list: 1 x Focusing Mask