Use this extension tube to get the correct image scale or the exact spacing required by the reducer or field flattener.The extension tube has T2 internal threads and T2 internal threads, which are used to solve the spacing problem in astrophotography and eliminate a series of focusing problems.The required spacing can be achieved by combining multiple expanders of different lengths.Type: T2 threaded extension tube for astronomical telescopeMaterial:aluminumcolour:BlackPackage Contents:1 x M48 Extension Tube Kits (3/5/7/10/12/15/20/30mm)Only the above package content, other products are not included.Note: Light 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.