Accurate positioning: There are 5 standard different drilling sizes, namely 1/4 inch, 3/8 inch, 5/16 inch, 7/16 inch and 1/2 inch. Three different size bushings, 2 x 1/ 4 inch, 2 x 5/16 inch, and 2 x 3/8 inch for creating different wood dowel joints. It is a tool used in woodworking to create precise holes for dowels. Precision Machining: Both side splints are made of industrial-grade aluminum alloy, and the drilling guide center is made of steel, which is machined by precision computer numerical control. When the middle bolt is turned, the aluminum on both sides are tightened at the same time to realize automatic center positioning, and the center error is within 0.002 inch. High precision: The self-centering positioning fixture is processed by precision computer numerical control machine tools. When you turn the middle bolt, the aluminum on both sides will tighten simultaneously and the sheet will be clamped evenly so that the hole punched is in the exact center. WIDELY USED: The self-centering dowel jig is perfect for some DIY projects, such as splicing two boards together. Make closet shelves that need flat connections, make some shelves, cabinets, desk, breakfast table, shutters for the garage, fix the door the kids accidentally broke, make floating shelves, install railings. Drilling Aid Marking Lines: Scores seen in front view for direct centering. Alignment can be done visually, making it easier to use. At the same time, clamp the board evenly so that the position to be pierced is accurately centered. Scale: Inch Scale Boring Size: 1/4 inch, 3/8 inch, 5/16 inch, 7/16 inch, 1/2 inch. Bushing Set: Two Each Of 1/4 inch, 5/16 inch And 3/8 inch. Size:12 x 4 x 6.5cm Material: metal colour: silver Package Contents: 1 x Self-Centering Positioning Fixture 2 x 5/16 inch Drill Bushing 2 x 3/8 inch Drill Bushing 2 x 1/4 inchDrill Bushing 1 x "L" Type Wrench Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.