TWSBI Eco Fountain Pen - Slate Blue with Onyx

A muted blue Eco with Onyx accents

The TWSBI Eco Slate Blue is a limited edition piston filling fountain pen in a muted blue-grey resin. Depending on lighting, it shifts between a cooler blue and a more neutral grey tone. It is finished with black Onyx plated trim and uses the standard Eco piston filling system.

What sets it apart

• Muted slate blue resin which changes in different lighting
• Black Onyx plated trim for contrast
• High capacity piston filling system
• Reliable steel nib with consistent flow
• Transparent barrel for ink visibility

Feel in the hand

The Slate Blue Eco has a restrained visual tone, with a darker blue-grey body and black trim that reduces contrast. It feels consistent and practical in use, and suits longer writing sessions where distraction-free design matters.

Who it’s for

• Writers who prefer muted, neutral colour palettes
• People building a consistent daily writing routine
• Users who want reliability without visual distraction
• Professionals who prefer understated stationery
• Anyone who wants a practical demonstrator with darker accents

Not for

• Users who prefer bright or highly saturated colours
• People wanting pocket sized or compact pens
• Those seeking cartridge or converter simplicity
• Writers looking for decorative or highly expressive designs

Practical tips

• Apply silicone grease only if the piston becomes stiff during use. Tools are included in the box.

FAQs

Is this good for beginners?
Yes, it's widely considered one of the best entry points because of its reliability and value

What’s different about the onyx nib?
The Onyx trim is primarily aesthetic and changes the visual contrast of the pen.

Does it come with ink?
No, this is designed for bottled ink use. It is designed for bottled fountain pen inks.

Can I take it apart?
Yes, TWSBI includes tools for maintenance, though it’s not needed often

What’s included

• TWSBI Eco Fountain Pen Slate Blue with Onyx
• Wrench
• Silicone grease
• Simple gift box
• Free nib tuning from LarryPOST

Ink pairing suggestions

• Blue-black inks to match the slate tone
• Dark blue inks for a consistent look
• Brown inks for contrast against the cool body
• Grey inks for a muted, low contrast palette

Build your practice

• Eco plated variants work well as a consistent writing system
• A simple pen wrap helps organise multiple pens
  
• Midori MD notebooks offer smooth paper and a visually soft creme paper

Specifications

• Brand: TWSBI
• Brand series: Eco
• Launch: March 2025
• Origin: Taiwan
• Nib: Black Stainless steel
• Nib sizes: EF, F, M, B, 1.1mm stub
• Filling system: Piston filler (1.8mL)
• Body: Transparent polycarbonate
• Cap: Twist
• Diametre: approx. 13mm
• Length: approx. 139mm (capped)
• Weight: approx. 21g (capped)
• Comparable size: Lamy Safari, Pilot Metropolitan

A slate blue Eco with a restrained, practical finish.