[Quality] High quality aluminum alloy 6061(drill guide) and die steel(bushing), high hardness and strength, good wear-resistant and durable to use. 【Range】Positioning dowel 1/4”（6mm）, 5/16”（8mm）, 3/8”（10mm）， Adjustable to clamp on different thickness of wood boards from 5/8" （17mm）to 2.4”(60mm) 【Design】The unique design is wavy on both sides. It is not easy to slip.It is a great tool set for both furniture factory and woodworking enthusiasts. 【Application】 It is an ideal tool for mortise and mortise layout and for drilling through fixed alignment pin holes. 【Package Included】 1 x Self Centering Dowelling Jig, 1 X 1/4" dowel Pin, 1 X 5/16" dowel Pin, 1 X 3/8" dowel Pin, 3 X 1/4" Drill Sleeve, 3 X 5/16" Drill Sleeve, 3 X 3/8 "Drill Sleeve.