on saleTWSBI ECO Fountain Pen - Cerulean

Product Code TW-M7449060

In Stock

out of stock

on saleTWSBI ECO Fountain Pen - Cerulean

Product Code TW-M7449060

In Stock

out of stock

Nib Guide

Not sure which size nib is best for you?

Try our Nib Nook tool to view and compare nib widths using our writing samples. Learn more ›

The TWSBI ECO fountain pen boasts an incredible value with its piston filling system and affordable price. Like many other TWSBI fountain pens, it features a crystal clear acrylic barrel so you can see your ink level, and a solid cerulean blue cap and piston knob. The pen cap has an inner cap to ensure a perfect seal when stored away. It is completed with silver trim and a silver stainless steel nib.

TWSBI's belief is that it is important to allow the user to disassemble and reassemble the pen and completely experience the traditional aspects of owning and using a fountain pen. These pens also come packaged with a wrench and silicone grease. Neither of these accessories are intended to be used immediately, as they are for long-term care and maintenance. Additionally, please use extra care if you choose to disassemble the nib and feed, as the feed is very fragile.

Fountain Pens
Blue, Clear

Whether or not the barrel of the pen is translucent, allowing you to see the ink and filling mechanism inside.

Body Material
Cap Rotations

For pens with a screw-cap closure, how many rotations it takes to uncap/recap the pen.

Cap Type

How the cap is opened/closed from the barrel of the pen. Some common options include Snap-Cap, Screw-Cap, Magnetic Cap, or Capless (no cap).

Compatible inks & refills

Which ink this pen will accept. Choices include bottled ink and various styles of pre-filled ink cartridges.

Bottled inks
Filling Mechanism

How the pen fills with ink. Click here to watch our video tutorial on common filling mechanisms.

Grip Material
Nib Size
Extra-Fine, Fine, Medium, Broad, 1.1mm Stub
Nib Color
Nib Material

Whether or not the cap fits securely onto the back of the barrel when open.


Whether or not the nib/tip can retract into the body of the pen (usually for click or twist-open style pens).

Diameter - Body
12.8mm (0.50in)
Diameter - Cap (without clip)
14.9mm (0.59in)
Diameter - Cap (with clip)
17.3mm (0.68in)
Diameter - Grip (mm)

Measured from the place most people choose to rest their fingers, which varies with each pen.

Length - Body

The measurement from the back end of the barrel to the tip of the nib.

131.6mm (5.18in)
Length - Cap
60.4mm (2.38in)
Length - Nib

The measured length of the visible portion of the nib when it is installed in the pen, from grip to tip.

18.5mm (0.73in)
Length - Overall (Closed)
138.8mm (5.46in)
Length - Overall (Posted)

When the cap of the pen is posted onto the back of the pen body, this is the measurement of the entire pen including the nib.

167.5mm (6.59in)
Weight - Body

If a converter is included with the pen, this weight is reflected in the total.

13g (0.46oz)
Weight - Cap
8g (0.28oz)
Weight - Overall (g)
Max Ink Capacity - Piston Vac

The maximum volume of ink that can fit in the pen when using the built-in piston or vacuum filling mechanism.


Customer Reviews

Based on 33 reviews
Linda C.
What a great pen!

My new Twisbi fountain pen is easy to fill, feels good in my hand, and writes smoothly. I highly recommend this pen.

Heather P.
Stub nibs are a ton of fun

I wanted to order pens in a variety of nib sizes to start out with, and the stub nibs on this Eco has been a pleasant surprise. It gives my handwriting some extra flair, and I can also fake some black lettering font with it. The cerulean blue color is quite pretty, and the ink capacity is so large you can use up almost a whole ink sample. I can see why so many fountain pen enthusiasts have a large collection of Ecos.

Wendy C.
Love My New Pen

I love my new TWSBI eco fountain pen. I really like the way you fill it, and it looks good with the ink in it. I am going to buy another one that is clear to use to try out all my sample inks. It doesn't post very well, but the feel of it while you are writing is great.

great pen

i really love this pen. There are some paper that i write on the pen has a hard time writing. however, for the most part, it is a great pen. i wanted a fine point pen, but i accidentally ordered an extra fine; however, it is still a wonderful pen, and want to order more.

Amy S.
Love this pen, troubles with several other TWSBI's

so this is one of my favorite TWSBI ECO's. because of the nib. I have developed an issue with TWSBI's, which I find disappointing. and that is inconsistency in feel, smoothness, and line width in their various pens. now that I have a medium amount of TWSBI pens, I feel that the #4 nib is my favorite. this is in the ECO, GO and Vac Mini. had a bad GO nib, in broad, that TWSBI replaced. horrible hard starts and skips, right out of the box. the broad they mailed me has no issue at all, but boy is it broad. can't use it for everyday writing of notes and stuff at work. I use if for headings to large writing of jotting down quick self reminders and such. back to the ECO: this one I bought in fine and it is smooth and perfect. like my VAC mini. Fine, smooth, soft, perfect, and constantly consistent. I have about 5 GO's. except for that one broad nib that was horrible out of the box, the GO's I have are fine and even two extra fine and are more like a fine. smooth comfy. not a single problem. have returned a few 580s that arrived with skipping or scratchy. completely different from the fine nibs in the VAC min and the ECO's and GO's. Have no idea why there would be such and issue. so have decided to settle on their pens with the #4 nib. the bummer about that is that my favorite feel, weight, length and such pen is the 580. and have two that are just ideal. but have had to return 3 so far. and it bothers me to return a pen, as I know the burden this places on a small business. but when I am just not gonna use a pen due to skipping or obnoxious scratchiness, then I just have to return it. I wish TWSBI could do a better job of even reasonable consistency in the nibs in their pens. I would buy them in every style and every color if they were better at this. The medium in my first TWSBI, a white ECO, is perfect. then the medium in the next pen I bought, the 580 Iris is much wider. usable so I kept it but much wider and wetter and cannot be used for various tasks. I also wish they did more colors in the 580's - which resin grip. I love the resin grip in the 580 and not so much the metal grips. Anyway, my experience with TWSBI is bitter sweet. keep trying with them, but dismayed at so many issues.

FAQs about Fountain Pens

How do I fill a fountain pen with ink? 8EDA1617-F73A-4DAF-8245-6D2BF4ABEB7B

It depends on the pen's filling mechanism, which you can find in the Technical Specs section above. 

Here's a quick definition of the most common filling mechanisms:

  • Cartridge - A small, disposable, sealed plastic reservoir that holds fountain pen ink. These come pre-filled with ink, and typically you just push to insert them into place and you'll be ready to write! Check out our quick guide here.
  • Converter - A detachable and refillable ink reservoir that allows you to use bottled ink in a cartridge-accepting pen. Typically you will install the converter into the grip section, dip the nib/feed into the ink, and twist or pull the converter knob to draw ink into the converter. Here's a video for how to fill a cartridge/converter pen using a LAMY pen as an example.
  • Eyedropper - A pen that utilizes the entire barrel as a reservoir for ink. Ink is directly filled into the barrel, allowing for a high ink capacity. Here's a video on how to do it!
  • Piston - A type of filling system that uses a retracting plunger inside a sealed tube to draw ink into a pen. They are typically either twist or push-operated. These pens cannot accept cartridges or a converter, and only fill from bottled ink.
  • Vacuum - A push-style piston that uses pressure to fill the large pen body with ink. They seal the ink chamber when closed, making it ideal for flying without risk of leaking. Check out our video on how to use a vac filler here.

Check out more info on these filling mechanisms including a video on how to fill each one on our blog.

How do I clean a fountain pen? 8EDA1617-F73A-4DAF-8245-6D2BF4ABEB7B

It depends on the filling mechanism, but it mostly comes down to flushing it out with water, and sometimes a little bit of Pen Flush if the ink is really stuck. 

It's a bit easier to show than to tell, so we've put together a few quick videos showing you the process:

How often do I need to clean my fountain pen? 8EDA1617-F73A-4DAF-8245-6D2BF4ABEB7B

We recommend a good cleaning every 2 weeks, and any time you change ink colors. 

Water will usually do the trick, but we recommend you use our Goulet Pen Flush if the ink has been left in the pen for a while and could have dried up, or when you’re switching ink colors.

My pen won’t write! What do I do? 8EDA1617-F73A-4DAF-8245-6D2BF4ABEB7B

First things first... make sure you have ink in the pen! Be sure that the ink cartridge or converter is seated properly in the pen, and that you aren't out of ink.

We always recommend you give your pen a good cleaning first, using our Goulet Pen Flush, or a drop of dish soap in some water. New pens often have some machining oil residue left in the feed, so a good cleaning often does the trick first.

If that still doesn't work, try priming the feed. This consists of either dipping your pen nib and feed in ink, or forcing ink from the converter down into the feed. 

If it’s still not working after that, please reach out to us so we can help! 

What's your return policy? 8EDA1617-F73A-4DAF-8245-6D2BF4ABEB7B

You can submit a return request within 30 days of your order date. You can read all our Return Policies here.

To initiate a return, please submit a request at the Return Portal. Our Customer Care team might reach out to you for more information.

Please note we are unable to accept a return of any Namiki or Sailor Bespoke fountain pen for any reason once it has been used with ink. Please thoroughly inspect and dry test the pen before use.