It adjusts the eyepiece position for a clearer image. Compatible with all types of telescopes, including reflectors and refractors, for observing star clusters, the Moon, planets, and other celestial objects. Constructed entirely from metal—no glue, no formaldehyde, and environmentally friendly. Features a threaded metal ring that screws on directly and remains securely in place. Designed to stay firmly attached without falling off or debonding over time. To select the correct size, measure the outer diameter of your telescope’s objective lens. For example: a 127SLT (146 mm outer diameter) requires a 160 mm solar film; an 8SE (235 mm outer diameter) requires a 250 mm solar film. Type: 80 mm Color: As shown Material: Metal Package includes: 1 composite membrane filter Note: Color may vary slightly due to screen settings and lighting conditions. Measurement tolerance: ±1–3 cm.