Features 1、Easy to install, perfect replacement for the old or damaged one, reliable to use. 2、Made from high quality aluminum alloy, which is wear‑resistant and not easy to damage. 3、Using fine workmanship CNC technology, the accuracy is higher, durable. 4、The female thread specification of the interface is M42x0.75mm, the male threadspecification is M42x0.75mm. 5、Various sizes of 3mm/5mm/7mm/10mm/12mm/15mm/20mm/30mm are suitable for different models. Specification Item Type: Lens Extension Tubes Material: Aluminum Alloy Color: Black Product Size: Approx.3mm / 0.12in, 5mm / 0.20in, 7mm / 0.28in, 10mm / 0.39in, 15mm / 0.59in, 20mm / 0.79in, 30mm / 1.18in, 12mm / 0.47in Application: Extend the focal length of the primary mirror of the astronomical telescope Extinction Treatment: Internal with extinction thread Interface Female Thread Specification: M42x0.75mm Interface Male Thread Specification: M42x0.75mm Package List 1 x 3mm Extension Tube 1 x 5mm Extension Tube 1 x 7mm Extension Tube 1 x 10mm Extension Tube 1 x 12mm Extension Tube 1 x 15mm Extension Tube 1 x 20mm Extension Tube 1 x 30mm Extension Tube