Takes compact to an entirely different level. Only .25" in diameter and 3 7/8" in length. Red aluminum construction with brass clip. Loaded with medium point black ink cartridge. Uses Fisher pressurized refill FP1211 (blue ink) or FP1241 (black ink). Hang packaged. Writes reliably under extreme conditions: over fingerprints, over grease, extreme cold (-50°C), extreme heat (+200°C), over wet paper, in a vacuum, and at any angle, even upside down.