Feature: 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 Tube1 x 5mm Extension Tube1 x 7mm Extension Tube1 x 10mm Extension Tube1 x 12mm Extension Tube1 x 15mm Extension Tube1 x 20mm Extension Tube1 x 30mm Extension Tube Note: 1. Please allow 1‑2in error due to manual measurement. Thanks for your understanding.2. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.