Product Description: Fully metal construction and anodizing aluminum process, durable for long for time use. Use this extension tube for getting the correct for image scale or the exact spacing required for reducers or field flatteners. The extension tube has a T2 interior thread and a T2 exterior thread for solving spacing problems in astrophotography and eliminates a range of focusing problems. Type: Astronomical T2 thread Extension Tube Male thread: M42*0.75mm Female thread: M42*0.75mm Link or extend tube length of the M42*0.75 Products Color: Black Length: 5mm 10mm 15mm 20mm Color: Black Please Note: This Combi are M42 (42mm) thread caliber, not M48 thread caliber Due to different production batches, the two paint color on the surface(Matte black; shiny black) are shipped randomly. Note: Please allow 0-2mm 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. Thank you! If you really care about these details, pls DO NOT order. Package Include: 1 x Extension Tube Kits(Size can be selected)