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, this pen only uses bottled ink, which is not included with this pen. Also available with Fine & Broad. 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. This pen can be entirely disassembled for the purposes of cleaning and servicing. Instructions and necessary tools are supplied with each pen. However, the disassembly feature is only there for experienced users and is not necessary for normal use. Disassembly is at your own risk!