Brief When you cannot get to the right focal plane for focusing with a camera or eyepiece. This extension tube kit solves this problem. You can use this extender with any camera or eyepiece or with various adapters. The M42 x 0.75 threads on both ends make it extremely versatile.Use this extender for obtaining the correct image scale or for the exact spacing required for a reducer or field flattener. You can reach the extension length required by combining several extenders of different lengths.Features:1, Fully metal construction and anodizing aluminium process, durable for long time use.2, M42x0.75 on both sides, eliminates a range of focusing problems3, The required spacing can be achieved by combining several extenders of differing lengths4, This extension tube for getting the correct image scale or the exact spacing required for reducers or field flatteners5, The extension tube has a M42 interior thread and a M42 exterior thread for solving spacing problems in astrophotography and eliminates a range of focusing problems.6, Type: Astronomical M42 x 0.75 thread Extension Tube7, Male thread: M42 x 0.75mm8, Female thread: M42 x 0.75mm9, Color: Black10, Net Weight: 364.5g / 12.85oz11, Length: 5mm 10mm 15mm 30mmSIZE: M42 2inchMaterial: aluminumPackage include:20 x M42 x 0.75 Thread Extension Tube(5mm,10mmm,15mmm,30mm)Only the above package content, other products are not included.Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.