Mitsubishi Pencil Pressurized Ballpoint Pen Refill Power Tank 0.7 Black SNP7. 10 pieces 990■ The outer box of the ballpoint pen is not included. Shaft diameter 7.95 x total length 111.5mm 10 refills Oil-based ballpoint pen refill Ball diameter: 0.7mm Size: Shaft diameter 7.95mm x total length 111.5mm [Writes with the power of air] This is a dedicated ink for pressurized ballpoint pens. Because compressed air is constantly pushing the ink out, you can write on wet paper, below freezing temperatures, and even upside down. The micro-protrusions on the surface of the spike ball at the tip of the Power Tank ballpoint pen grip the paper firmly, allowing the ink to be written on and grip the paper firmly, so you can write firmly on smooth surfaces such as photos and drawings.