The Tech Force Pen is a solid housing for the HI-Tec C Ink Cartridge. Extremely popular among architects, artists, students, and designers, the cartridge is noteworthy for its C Ink composition, tip design, and fine line capability. The Tech Force Pen comes with a sleeve etched with metric and imperial ruler indications. The pen glides into the ruler sleeve where it is held in place by pneumatic pressure. When pulled from the ruler sleeve the escaping air makes a characterist