Features: Made of premium metal & aluminum, durable & long time service. Smooth surface for effortless mount. Diaphragm control of the lens is set manually. Internal thread size: SCT thread (2 in, 24 teeth thread), depth of internal thread: 6mm,external thread spec: M48x0.75mm. Just reversely connect it to the machine body, so you can achieve the nomal lens micro shooting effect. Package Includes: 1x Reverse Mount Adapter Ring Specifications: Material: Metal+Aluminum Internal thread size: SCT thread (2 in, 24 teeth thread) Depth of internal thread: 6mm Specifications of external thread: M48x0.75mm Depth of external thread: 4mm Flange distance: 8mm Diameter of optical hole: 45mm Inner wall of through-light hole: extinction thread note: Please allow 1-3cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item.