TWSBI Nib and Line Comparison

TWSBI Nib and Line Comparison

In our recent blog post, An Introduction to TWSBI Pens and our YouTube video all about TWSBI, we talked about some of the different models of TWSBI fountain pens and gave a brief overview on TWSBI and their history making fountain pens. In this blog post, we'll be taking a closer look at the actual different nibs available on TWSBI fountain pens, comparing how they write and how their nib sizes differ. If you have decided on a TWSBI model and are trying to choose between different nib sizes, this article may help you decide which nib size is the right one for you! 

Nib Sizes vs. Nib Numbers

Although there are many TWSBI fountain pens, quite a few different models and perhaps more special limited edition colors than you can keep track of and covet, there are just three different TWSBI nibs to choose from--the #4, 5 and 6 nibs. These nib numbers differ from nib sizes in that they refer to the actual size of the nib (as a whole) as opposed to the size/width of the tip of the nib. So when we are talking about nibs, they can be referred to by their nib number, indicated on a numerical scale, and by their nib size. For example, a #6 EF (Extra Fine) nib, is quite a large nib with a small tip that produces a thin line when writing. Nib sizing matters for the type of writing you want to do with your pen and nib numbering can matter if you prefer a larger nib when writing or if you like to swap your nibs across your pens, you'll need to confirm that your nibs are the same size number. 

How can I tell what nib size my TWSBI is?

If you already have a TWSBI and you're not sure what nib size you have, you can take a minute and examine your nib. With the nib facing up, you will see the tines of the nib leading to the tip of the nib and on the top face, you'll see TWSBI and its logo engraved into the metal. Just below these, near where the nib and the grip section meet, you'll be able to see the nib size engraved. On a Diamond 580 and Diamond Mini, you can see the engraving easily but on an ECO nib, which is inserted deeper into the grip section, the engraving is almost completely hidden and you may need to use a flashlight and magnifying glass to be able to make out the tops of the engraved letters. 

How and Why We Do Our Nib and Line Comparisons

In our shop, we have all of the possible different TWSBI nibs inked up and ready for you to try since we understand that finding the right nib size is as personal a choice as it gets when it comes to stationery! For those of you who can't make it to our shop, we get questions all the time asking us to make a recommendation on a nib size, which is why we began making our Nib and Line Comparison videos on our YouTube channel.

In these videos, we write with all the different nib sizes available on a specific fountain pen and draw comparisons between the thickness of the line you get from the fountain pen and the thickness of a felt tip fine liner. Out of all the pens we have available at our fingertips, we use these Copic Multiliners because they are pretty precise in their line widths and also draw a consistently thick line given you are applying even pressure as you are holding the pen. While it is possible to measure the thickness of each line using a caliper for a measurement of the exact thickness, we've chosen to approximate the thickness visually since most people don't have a caliper at home. 

For this nib and line comparison, the paper we used was Tomoe River 52gsm and all pens were inked with Sailor Black ink. 

TWSBI #4 Nib: Line Comparison

If you've read our previous blog post, you'll know that most TWSBI pens come with the #4 nib found on the TWSBI Go, SWIPE, ECO, ECO-T, Diamond Mini and Vac Mini models. 

Nib Size  Line Width Approximation
Extra Fine <EF> 0.4 mm
Fine <F> 0.5 mm
Medium <M> 0.8 mm
Broad <B> 1.0 mm

TWSBI #5 Nib: Line Comparison

The TWSBI #5 nib is found on the TWSBI Diamond 580. 

Nib Size  Line Width Approximation
Extra Fine <EF> 0.4 mm
Fine <F> 0.6 mm
Medium <M> 0.8 mm
Broad <B> 1.0 mm

TWSBI #6 Nib: Line Comparison

The TWSBI #6 Nib is found on the TWSBI Vac700R.

Nib Size  Line Width Approximation
Extra Fine <EF> 0.35 mm
Fine <F> 0.5 mm
Medium <M> 0.7 mm
Broad <B> 0.9 mm

Overview of TWSBI Nib and Line Comparison

Overall, TWSBI nibs are surprisingly similar and consistent in their line width. The #4 nib and the #5 nib in particular are very close. The #7 nib, found on the Vac700R, is the nib that feels the most different. Generally speaking, the nib on the Vac700R is a bit finer than the nibs on the other models. It is also a stiffer feeling nib, which can contribute to the fineness. 

TWSBI Stub Nibs

As I was setting out to do this nib and line comparison, I had not planned on writing anything much on their stub nibs, but while writing with each nib, I began to see a clear distinction between the different TWSBI stub nibs. As you can see from the photo above, the stub on the left, which is found on the #4 nib and the #6 nib has more of a curved shape on the tape as opposed to the sharpened edge on the tine of the #5 nib. As a result, the writing produced when writing with the #5 nib (the nib found on the Diamond 580) has thicker and bolder lines more characteristic of a typical stub nib. So, if you are looking for a classic experience of writing with a stub nib, I would recommend choosing the stub on the Diamond 580 over the stub on all other TWSBI fountain pens. 


Hope this blog post was helpful to you for choosing your next TWSBI nib size! 


  • James

    Very helpful, thank you!

  • Massimiliano della Rovere

    Very useful article, thanks!

    One little improvement hint: in the picture belonging to the stub comparison, it would be useful to show horizontal strokes, too, in order to compare their thickness to one another and to the vertical stroke.

  • Farha

    Extremely detailed and exactly what I was searching for!

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