Item Type: Telescope Adapter Ring Material: Aluminium Alloy Internal Thread Specification: M48 x 0.75mm External Thread Specifications: M42 x 0.75mm (Commonly Known As T2 Thread) Thread Depth: 3mm Flange Distance: 4mm Total Length: 7mm Diameter of Inner Hole: 39mm Outer Frame Diameter: 50.7mm0.1mm Package List 1 x Telescope Adapter Ring 1 x Plastic Storage Box 1Seamless Connection: This telescope adapter ring features seamless connection, M42 and M48 fittings can be connected together. 20.75mm Thread: This M42 to M48 coupling ring adapter possesses M42x0.75mm external thread and M48x0.75mm internal thread. 3Aluminium Alloy: This M42 to M48 ring adapter is made of aluminium alloy material, sturdy and durable. 4Easy Installation: This telescope adapter ring can be easily installed, very flexible and convenient to use. 5Extinction Treatment: The inner wall of this telescope lens filter ring adapter adopts extinction treatment, avoid radiation affecting the image.