Fully metal construction with aluminum processing for durable, long-term use. This extension tube helps achieve the correct image scale or precise spacing required for reducers or field flatteners in astrophotography. Features a T2 internal thread and T2 external thread to resolve spacing issues and reduce focusing problems. Multiple extension tubes can be combined to achieve the desired length. Type: Astronomical Telescope T2 Thread Extension Tube Size: M42 x 0.75 Extension Tube Heights: 3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm Use this extension tube when unable to reach the optimal focal plane with a camera or eyepiece. Compatible with various cameras, eyepieces, and adapters. The M42 x 0.75 threads on both ends provide versatile connectivity. Color: Black Material: Aluminum Package Contents: 8 x M42 x 0.75 Thread Extension Tubes (3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm) Note: Light and display settings may cause slight color variations between the image and actual item. Measurement allowance is +/- 1-3cm.