Fully metal construction and aluminum processing for long-term use. Use this extension tube to achieve the correct image scale or precise spacing required for reducers or field flatteners. The extension tube features a T2 internal thread and a T2 external thread, helping to resolve spacing issues in astrophotography and eliminate various focusing problems. The desired spacing can be achieved 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 Color: Black Material: Aluminum Why use this extension tube? When you are unable to reach the correct focal plane with a camera or eyepiece, this extension tube kit provides an effective solution. It can be used with various cameras, eyepieces, or adapters. The M42 x 0.75 threads on both ends offer excellent versatility. Use this extension tube to achieve the correct image scale or exact spacing needed for a reducer or field flattener. Required extension lengths can be achieved 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: Lighting and display differences may cause slight color variations between the image and the actual item. Measurement error allowed is +/- 1-3 cm.