Fully metal construction and aluminum process for long-term use. Use this extension tube to achieve the correct image scale or exact spacing required for reducers or field flatteners. The extension tube features a T2 internal thread and a T2 external thread, helping to solve spacing issues in astrophotography and reduce focusing problems. Achieve the required spacing by combining multiple extension tubes of different lengths. Type: Astronomical Telescope T2 Thread Extension Tube Size: M42 x 0.75 Extension Tube Lengths: 3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm When focusing cannot be achieved with a camera or eyepiece, this extension tube kit provides a solution. Compatible with various cameras, eyepieces, and adapters. The M42 x 0.75 threads on both ends offer high versatility. Use this extension tube to obtain the correct image scale or precise spacing for optical accessories such as reducers or field flatteners. Customize the extension length by combining different spacers. Color: Black Material: Aluminum Package Contents: 8 x M42 x 0.75 Thread Extension Tubes (3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm) Note: The package includes only the items listed above. Other products are not included. Lighting and monitor settings may cause slight color variations between the image and the actual product. Measurement error allowed is +/- 1-3 cm.