TWSBI fountain pens are loved for their high quality and affordability, offering advanced filling mechanisms normally reserved for much more expensive fountain pens. The TWSBI ECO (short for "economical") provides the same high-quality, high-capacity piston filler as the TWSBI Diamond 580 at an even lower price. It features a sleek, transparent barrel and a hexagonal screw-on cap that can be posted securely on the back of the pen. The 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. There's 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.

This limited-edition pen features a marbled black cap and piston knob, accented with a bronze-colored nib and trim. The pattern of the marbling varies from pen to pen, and no two pens are exactly alike.

In keeping with their philosophy of promoting the traditional experience of using a fountain pen, TWSBI has designed this pen to be completely self-serviceable. It comes with a wrench and a vial of silicone grease you can use for at-home maintenance.