Fully metal construction with anodized aluminum, durable for long-term use. Use this extension tube to achieve the correct image scale or precise spacing required for focal reducers or field flatteners. The extension tube features T2 internal and external threads to resolve spacing issues in astrophotography and minimize focusing problems. Required spacing can be achieved by combining multiple extension tubes of varying lengths. Type: Astronomical Telescope T2 Thread Extension Tube Thread Size: M42 x 0.75 Extension Tube Lengths Available: 3 mm, 5 mm, 7 mm, 10 mm, 12 mm, 15 mm, 20 mm, 30 mm Why use it? When the camera or eyepiece cannot reach the optimal focal plane for sharp focus, this extension tube kit provides a solution. It is compatible with cameras, eyepieces, and various adapters. The M42 x 0.75 threads on both ends ensure broad compatibility. Use this extender to achieve accurate image scale or exact spacing for focal reducers or field flatteners. Customizable extension length is possible by stacking multiple tubes of different sizes. Color: Black Material: Aluminum Package Contents: 8 x M42 x 0.75 Thread Extension Tubes (3 mm, 5 mm, 7 mm, 10 mm, 12 mm, 15 mm, 20 mm, 30 mm) Note: The actual product color may vary slightly due to lighting conditions and display settings. Measurement tolerance: ±1–3 mm.