eBay 112L / min Pneumatic Air Scribe Hammer with Hose Engraving Pen Engraving Tool Specification: Vibration frequency: 3400 / min Air consumption: 112L / min Air inlet size: 1/4 " Length: 180mm Working pressure: 60-90psi Weight: Approx 130g Feature: 1. Quick lettering, use for flexible and comfortable. 2. Pen needles is made of special alloy steel, good durability. 3. Depending on the difference of material ,depth can be up to 1mm. 4. Works great on metal, wood, plastic, glass, stone…