TWSBI ECO Cosmos Blue with Onyx Fountain Pen

Drawing inspiration from the quiet depth of the night sky, the ECOCosmos Blue with Onyx edition captures the serene beauty of a starlit horizon. Its cap and piston knob are crafted from rich, deep blue resin, subtly marbled to evoke swirling cosmic clouds contrasted by sleek onyx-black accents that ground the design in modern sophistication. The transparent demonstrator barrel reveals the inner workings of TWSBI’s precise piston-fill system, offering both visual intrigue and practical insight into the ink level within.

Polished black hardware and the signature TWSBI red emblem on the finial complete the pen’s celestial aesthetic. The stainless steel nib, finished in matching black, delivers a smooth and consistent writing experience, with a balance of gentle feedback and dependable ink flow. Designed for extended writing sessions, the high-capacity piston-filling mechanism minimizes the need for frequent refills, while the screw-on cap with its secure O-ring seal protects against leaks and evaporation.

As with all ECO models, the Cosmos Blue with Onyx can be fully disassembled for cleaning and maintenance (tools included), though TWSBI recommends this only for experienced users.

Key Features

• Unique ‘Cosmos’ marbled cap with onyx trim
• Polycarbonate construction creates scratch resistant, resilient and crystal clear finish
• Hexagonal shaped cap and piston mechanism tip
• Twist action piston fill mechanism
• Stainless steel (in Bronze) nib with intricate TWSBI logo and detailing
• Screw close cap
• Rubber O-ring prevents leakage and drying
• Gently tapered grip section
• TWSBI logo button on end cap
• TWSBI presentation box
• Lifetime manufacturer warranty
• Dimensions (Closed): L 140mm x D 15mm
• Dimensions (Posted): L 168mm x D 15mm
• Diameter taken at widest point (not including clip)
• Weight: 21g