Features: Quick lettering use for flexible and comfortable. Pen needles is made of special alloy steel well durability. Depending on the difference of material to decide the depth. Works well on metal wood lastics glass stone porcelain and other hard material. This configuration is nice for marking tools parts and more. Great for final cleaning and polishing of dies jewellery and for hobby. Notice: When using the tool add the pneumatic oil regularly every 2-3 hours at a time (about 5-6 drops). Actual color may be slightly different from the image due to different monitor and light effect Please allow 1-3cm deviation due to manual measurement Specification: Type:Pneumatic Grinding Pen Material: Plastics + Alloy steel Length: 143mm Chuck Size: 3mm Air Inlet Thread: 1/4-28UNF Free Speed: 70000 rpm Air Pressure: 90psi