Self-Centering Dowel Clamp Type: Straight Hole, Maximum Backer Plate Thickness: 1-3/4" (45mm), Drill Guide Diameter: 6mm, 8mm, 10mm Easy to use adjust the position of the feet to accommodate boards of different thicknesses, quickly and easily punch holes in the sides of boards with good verticality and greater hole punching accuracy. 3 Sizes of Drill Bushings - The package comes with 3 different sizes (6mm/8mm/10mm) of drill bushings, which can easily drill different size holes to meet various support needs. Wide range of applications - Used for precise positioning when punching holes in the sides of boards, quickly positioning openings allowing seamless splicing between boards. HIGH QUALITY Made of aluminum alloy with surface oxidation treatment, high hardness, wear-resistant, rust-proof, sturdy, durable and very suitable for use.