Early thoughts on the Moonman S5 fountain pen.

Occasionally a pen comes along that looks so enticing, full of potential and such good value that I am unable to resist buying it. Well, quite often, tbh. In this case, it was the Moonman S5, a clear acrylic demonstrator, eye-dropper pen which comes with an eye-dropper and three different nibs all for under £24.00.

What interested me particularly was the statement that it had an Extra Fine nib and two additional nibs in Medium and Broad. After watching one YouTube review, I gathered that the Broad nib was a stub of about 1mm width. But subsequently, from examining the nib and watching some more reviews, it transpires that the Broad nib is in fact an Oblique, which for me as a lefty overwriter, turns out to be brilliant news.

The Unboxing.

The pen comes in a nice black tin with gold lettering, held shut by a cardboard sleeve, with a nib motif and an M for Moonman.

The set comes in this black tin.

Inside the tin, in sturdy cushioned recesses, are the pen (in a polythene sleeve), the eye-dropper and the two additional nibs. There is a folding sheet of diagrams for filling various types of fountain pen, including eye-droppered pens.

What’s in the tin. (Also some instructions, not shown).


This is a clear, acrylic pen, with a screw on cap (taking three complete turns), no pocket clip but a jewel-like roll stop set in a metal band on the barrel. The band has the name MOONMAN laser-etched against the shiny background. The grip section is comfortably shaped with a very slight hour-glass contour and is in a patterned acrylic with a crazy-paving effect, in a mixture of colours – green, blue, purple, white and brown against a black background. I thought it looked a bit incongruous at first, as though it was for a different pen but I quite like it now. It comes alive and sparkles under the bright light of a loupe.

The Extra Fine nib. The roll-stop jewel is centred in this picture.

The barrel has a distinctive taper to it before flaring out at the end like a fishtail, into a flat base, on which the pen can be stood up. It looks a bit like a lava lamp when upright. The cap also has a flat top, which is useful if you wish to stand the pen upside down for a minute or two, to allow ink to make its way to the feed after filling.

The pen standing in lava-lamp mode.

The barrel shape actually makes the pen very comfortable to hold unposted but for me, I prefer to post the cap whereupon the slight extra weight, length and girth at the back end, make it supremely comfortable. The cap posts very deeply and securely, if given a little twist.

The S5 with cap posted.

Size and weight.

I would call this a medium sized pen. It measures approximately 136mm closed, 123mm uncapped and 136mm posted. Weight (when about one third full of ink) is around 18g, as to 14g for the pen uncapped and 4g for the cap.

The three nibs.

I tried the Extra Fine nib first, dipped but not filled. This one has gold coloured plating, some scroll work and logo and the words MOONMAN SUPER QUALITY.E I am not sure what the E is for. On a brief dip test, the nib wrote smoothly but with an extremely fine line. I wrote about four lines with it but did not leave it on for very long and in hindsight, did not push it to try for any line variation, before unscrewing it and fitting the Medium nib.

The fitted Extra Fine nib is seriously fine, but YMMV, as one YouTube reviewer found little difference between the fine and medium.

The Medium nib had rather less markings on the nib – just a pattern within a circle but no text or width designation. It wrote well – significantly darker than the Extra Fine and with a typical medium-fine width. Again, in my excitement to try them all, I wrote only about four lines before switching to the widest of the three nibs.

The two additional nib units, each with a housing and a grey rubber O ring. Be careful not to lose the ring.

The Broad nib (again with only the floral pattern in a circle and no markings) is an Oblique. Looking at the face of the nib, tip upwards, the tip slants downwards to the left about 15 degrees and is what I believe is called a Left Foot Oblque, looking like a left foot. It produces a line of roughly 0.6 – 0.8mm maximum width, which is lovely.

This was for me, the best of the three nibs and I liked it so much that I have not taken if off since. It was like Goldilocks finding the bed that suited her best, or the glass slipper finding Cinderella.

For me, the Oblique nib writes super-smoothly, with a nice flow. I inked the pen (as I ink most of my pens the first time), with Waterman Serenity Blue. It provides a broad line with some subtle line variation. It takes just a little practice to find its sweet spot and then to keep it at the same angle as you write.

Writing sample with the Oblique broad nib, Waterman Serenity Blue ink and a Leuchtturm A5 journal. Bliss.


Filling is simplicity itself. You just unscrew the barrel and drop some ink into it with an eye-dropper or a syringe if you prefer. I use large soft plastic pipettes bought from an art shop. I put a little silicone grease on the threads before re-attaching the barrel although there is a O ring there and the grease might not be necessary. Then leave the pen to stand, nib down for a minute or so while the ink fills the feed. I have not yet measured the capacity.

A dream combo.

Likes and dislikes.

The only negative I found so far, is the jewel roll-stop. It is not that I have anything against the jewel itself, but I found that it gets in the way of my grip. When the pen arrived, it was aligned with the nib but once I started fitting different nibs into the section, and then screwing the section back on to the barrel, it was “jewel roulette” to see where the jewel would end up, in relation to the top of the nib: not that being in the 12 o’clock position would necessarily be the best position for me. But, by good fortune, I found that when the oblique nib is screwed in, the jewel finishes up at about the nine o’clock position (viewed facing the nib head-on) which for me is perfect and the jewel is completely out of the way.

If this does not work for you, I hope it may be possible to prise the jewel out of the cap band, or even to file it flat. Alernatively perhaps with the preferred nib unit screwed in, the nib and feed could be pulled out of the housing and replaced in different alignment to the jewel. I have not tried this yet.

Note the roll-stop jewel seen here at about the 9 o’clock position which is ideal for me.


This is my first foray into the Moonman brand. I seem to have struck gold first time. I am thrilled with the pen and its Oblique nib. Writing with this, with Waterman Serenity Blue and my Leuchtturm A5 journal is a dream combination.

I have not filled the pen completely as I will try some more adventurous colours next. It is easy enough to swap out the nibs too and I need to give the others a proper go at some stage. Having found that the Oblique nib is capable of such smooth and pleasurable writing it just remains to test longer term for hard starts and for possible burping of ink, which eye-dropper pens sometimes suffer from. I hope I have not spoken too soon but so far all is looking good. At £23.99 I think this represents great value. If any bad behaviour occurs to take this grin off my face, I shall add an update.

Lovely smooth writer, with effortless line variation (see the capital A and V).

12 thoughts on “Early thoughts on the Moonman S5 fountain pen.

  1. That’s a really interesting pen. A lot of demonstrator/clear pens don’t quite do it for me, perhaps because the workings inside the barrel feel too busy (it’s what keeps me from trying a TSWBI), but this eyedropper filled pen just looks so good. It is useful, too, to read your experience with the nibs. And you can’t beat a photo of a pen resting on a hand-written page!

    Liked by 1 person

    1. Thanks! I am enjoying this one a lot. It is very comfortable and writes like a dream. Also quite flattering to my handwriting!
      The eyedropper filling is fun…just chuck more ink in, like adding to a stew.


  2. I really enjoyed this review. I love the idea of getting additional nibs in the same box, what a great way to offer some variation with the pen. Great review.

    Liked by 1 person

    1. Thank you very much. This is a nice set and it is easy to swap the nibs around. It is unusual to find an oblique nib these days, on a pen at this price level and I have been very pleasantly surprised at how smoothly it writes.The filling system is fun too.


    1. The nib unit might be a bit tight the first time, or might have got stuck due to dried ink. You just grip the nib firmly between thumb and finger, from the front and back, (not the sides), holding it so that the nib and the feed do not get out of alignment, then unscrew the pen from the nib, rotating the pen anti-clockwise whilst gripping the nib and holding it still. Good luck!


  3. Do you have the problem with the broad nib where you have to push it down on the paper with a bit of force before the ink will come out to write smoothly? Also, as soon as I lifted up my s5, if I wait a bit before writing again, I will have to push it down with force again to let the ink come out. I’m wondering if it is my nib’s problem or I’m just not used to using a stub nib to write. I just can’t seem to get a constant smoothness of ink from writing.

    Liked by 1 person

    1. Thankyou. The broad nib in my Moonman is a left oblique. I do need to just touch it lightly to the paper, to check that ink appears on the paper before I start writing. This is to make sure that I am holding it at the correct angle. But I do not need to press down hard…only a light touch just to wake up the nib. If you observe the nib closely with a magnifying glass while doing this you can see what’s going on, check you are holding it right at the sweet spot and see the ink flow as the tines part slightly. Mine writes like a dream and it is one of my favourite pens…at any price.


  4. Are there any additional compatible nibs available to purchase? I am looking at buying one through work (any good affordable wide grip fountain pen – ideally eyedropper for capacity).
    I have one of these at home (my 3rd pen) and appreciate the wide grip but I find it leaks into the cap despite me using silicone grease this time (newby) and the leak appears to come from on top of the nib at the join to the barrel.
    I’ve had other plastic moonman pens(if it really is) but found that the nib holder snapped immediately at the external ring, they sent me replacements but it was still leaking all over so I hardly use it despite it eing smale
    My original pen is a heavier jinhao 8802 that I love (no nib issues) but I dont think it is compatible with being an eyedropper due to it being metal and I really like the eydropper idea as cartidges are hard to fully clear when swapping ink and the extra capacity wou be great.
    If I’m doing anything glaringly wrong, please let me know so I can correct it.
    I’m looking for a fat pen asap for work and if I can find extra nibs to purchase then this one could be it.


    1. I am not aware of any compatible nib units available for the Moonman S5 eye dropper pen.
      If you want a large capacity, large girth eye dropper pen, take a look at some Opus 88 models. The Opus 88 Demonstrator is very large but cost around £100 when I got mine.
      But if you need large ink capacity without such a wide girth then try TWSBI models such as the Eco, Diamond 580 (piston fillers) or VAC 700 (vacuum filler).


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.