Quick lettering, use for flexible and comfortable. Pen needles is made of material, good durability. Depending on the difference of material to decide the depth. Works great on metal, wood, plastic, glass, stone, porcelain and other hard material. This configuration is great for marking tools, parts and more. Name:Pneumatic grinding pen For: final cleaning and polishing of dies, and jewelry and for hobby Color: color Material: plastic + steel Length: 143mm Chuck size:3.0mm Free speed: 70000 rpm Air pressure: 90psi Air inlet thread: 1/4inch Package: 1* -mold type air grinder 30* alloy grinding head 10* grinding wheel head 2* wrench 1* box Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.