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 Heights: 3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm Color: Black Material: Aluminum This extension tube kit helps when the correct focus plane cannot be reached 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 extender to obtain the correct image scale or precise spacing for a reducer or field flattener. Adjust the total extension length by combining several extenders of different 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 color variations between the image and the actual item. Measurement may vary by +/- 1-3 cm.