Specification: Interface has a locking mechanism, easy to install. It is light and convenient, easy to install and easy to take. Used for lengthening the shank of milling cutters, engraving or trimming machine accessories. Type: Extension Rod Material: Carbon Steel Features: Durable, Practical, Turning Tool Shank Diameter: 1/4", 6mm, 8mm, 12mm, 1/2" Size: 8.2cm x 2.7cm/3.23" x 1.06" (Approx.) Specification: 1#: Extension rod 6mm to 6mm 2#: Extension rod 1/4 inch to 1/4 inch 3#: Extension rod 1/4 inch to 8mm 4#: Extension rod 8mm to 12mm 5#: Extension rod 8mm to 1/2 inch 6#: Extension rod 8mm to 8mm 7#: Extension rod 12mm to 12mm 8#: Extension rod 1/2 inch to 1/2 inch Notes: Due to the light and screen setting difference, the items color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Includes: 1 x Extension Rod (Others Not Included)