TWSBI fountain pens are loved for their high quality and affordability, offering advanced filling mechanisms normally reserved for much more expensive fountain pens. The Diamond 580 features a modern, eye-catching design, with a transparent body that shows off the pen’s inner workings. Its faceted barrel catches light and makes your ink shine, and it also helps keep the pen from rolling away. The high-capacity piston filling mechanism is easily operated by twisting the knob at the end of the barrel counter-clockwise to extend the piston, submerging the nib in ink, then screwing the knob tight to retract the piston, drawing ink into the pen straight from the bottle—no need for cartridges or a converter! Be careful, operating the piston while ink is in the pen will cause ink to leak out of the pen.