Koloro

As an Amazon Associate I earn from qualifying purchases.

An eyedropper-filled pen with a shut-off valve, giving one of the largest ink capacities you can buy without switching to a dedicated eyedropper conversion.

A solid mid-range option once someone has decided fountain pens are a habit worth investing a bit more into.

Specs

Filling systemEyedropper

Ink capacity~2.5–3 ml (full barrel)

Nib optionsEF, F, M, B (steel or gold)

MaterialAcrylic + ebonite feed

Typical price~$140–170

How long has your Koloro been inked?

Inktend counts the days and reminds you when it's time to clean.

Track it →

About Opus 88

A Taiwanese maker best known for popularizing the eyedropper filling system at accessible prices: a shut-off valve design lets the entire barrel hold ink without the leaking risk eyedropper pens traditionally carried. This model, Koloro, dates to part of Opus 88's core eyedropper lineup.

See all Opus 88 products →

How to fill the Opus 88 Koloro

The entire barrel doubles as the ink reservoir: unscrew the section, drip ink directly into the barrel with a bottle's eyedropper or a syringe, then reassemble. This is the highest-capacity filling method available, often multiple times what a piston holds, but it also means more ink is at risk if a seal ever fails, so silicone grease on the threads is essential.

Choosing a nib size

Nib size determines line width, not writing pressure: fountain pens are meant to glide, never press. Extra-fine (EF) suits small, dense handwriting and thin paper; fine (F) is the most broadly recommended default; medium (M) shows more ink character and shading; broad (B) and stub grinds favor bold, expressive strokes and calligraphy-adjacent writing. The Koloro's gold nib will also flex slightly with pressure, giving line variation that a steel nib of the same size won't produce.

Keeping it clean

Because Opus 88 Koloro holds a larger ink reserve, a full flush every 4–6 weeks (or whenever you switch colors) keeps the feed running cleanly. Inktend's cleaning reminder is tuned to a 21-day baseline and adjusts naturally to how often you actually refill.

Pairing inks with the Koloro

High-capacity fillers like this one are the natural home for sheening and shading inks; you'll actually see the color develop across a full page instead of running out mid-paragraph.

Browse the full ink library →

Frequently asked questions

How do I fill the Opus 88 Koloro?

Unscrew the barrel and fill it directly with a bottle's dropper or a syringe. Highest capacity of any filling method, but seal it with silicone grease to avoid leaks.

What nib size should I get for the Koloro?

Fine (F) is the safest default for a first pen. Go finer for small, dense handwriting; go broader if you want more ink character and shading.

How often does the Koloro need cleaning?

Every 4 to 6 weeks, or whenever you switch ink colors, whichever comes first.

Is the Opus 88 Koloro good for beginners?

It can work as a first pen if you're comfortable spending a bit more to start.