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 reducing a range of focusing problems. The required spacing can be achieved by combining several extension tubes of different lengths. Type: Astronomical Telescope T2 Thread Extension Tube Size: M42 x 0.75 Available Lengths: 3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm Color: Black Material: Aluminum This extension tube kit helps when you cannot reach the correct focal plane with a camera or eyepiece. It can be used with various cameras, eyepieces, or adapters. The M42 x 0.75 threads on both ends provide high versatility. Use this extension tube to achieve the correct image scale or precise spacing for reducers or field flatteners. Achieve the desired extension length by combining multiple tubes of varying sizes. Package Contents: 8 x M42 x 0.75 Thread Extension Tubes (3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm) Note: Light and display differences may cause slight variations in color between the image and the actual item. Measurement error allowance: +/- 1-3 cm.