Specification Brand : YOUTHINK BulletPoint1 : Eliminate focus problems: The extension tube has M48 female thread and M48 male thread, which is used to solve spacing problems in astrophotography and eliminate focus problems in series. BulletPoint2 : Various combinations: The required spacing can be achieved by combining multiple extension rings of different lengths. You can use 1, 2, 3 or 8 extension rings depending on your needs. BulletPoint3 : Aluminum alloy material: all metal construction and anodized aluminum process, sturdy, this extension tube allows you to get the image scale or spacing you need for your reducer or field flattener. BulletPoint4 : Eliminate excess light: The female thread design eliminates stray light and reflected light, making the image clearer and more great. BulletPoint5 : Type: Astronomical Telescope Extension Tube with M48 Thread, the height of the extension tube is 3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm. ItemName : Extension Tube 8-Piece Set, High Precision, 3/5/7/10/12/15/20/30mm, Telescope Extension Tube, Eliminates Focus Problems, M48X0.75, Telescope Accessories, For Astronomical ItemPackageDimensions_Height : 6 centimeters ItemPackageDimensions_Length : 16 centimeters ItemPackageDimensions_Width : 10 centimeters ItemPackageQuantity : 1 ItemTypeKeyword : camera-lens-extension-tubes Manufacturer : YOUTHINK ModelName : YOUTHINKmfro4ixhga ModelNumber : YOUTHINKmfro4ixhga PartNumber : YOUTHINKmfro4ixhga ProductDescription : 1. Eliminate focus problems: The extension tube has M48 female thread and M48 male thread, which is used to solve the spacing problem in astrophotography and eliminate the series of focus problems. 2. Eliminate excess light: The female thread design eliminates stray light and reflected light, making the image clearer and more . 3. Various combinations: The required spacing can be achieved by combining several extension rings with different lengths. You can use 1, 2, 3 or 8 extension rings as you need. 4. Type: Astronomical telescope extension tube with M48 thread, the height of the extension tube is 3mm, 5mm, 7mm, 10mm, 12mm, 15mm, 20mm, 30mm. 5. Aluminum alloy material: All metal construction and anodized aluminum process, STURDY, with this extension tube, you can get the image scale or spacing you need for your reducer or field flattener.