If you need opaque colours for lettering or visualizing, the AcrylicOne from the large Neuland range of markers is the right choice. Naturally, these are also refillable, and hence also the right choice economically as well as ecologically.
We have provided some instructions to make refills as easy as possible and eliminate problems:

A. Preparation

Before refilling, please lay an underlay for the valve and marker nib.
To keep your hands clean, it is advisable to wear disposable gloves.

1. Shake the refill well

The two marbles within the refill should be audible as these ensure
that the colour is evenly mixed within the refill.

2. Open the marker

Carefully unscrew the cap at the thread and place on the prepared underlay.

3. Remove the valve

Carefully draw out the valve and place on the prepared underlay.

4. Fill the marker

Fill the pen body with the colour by simply squeezing the refill gently!

5. Reclose the marker

Reposition the valve and screw the pen cap back onto the pen body.

6. “Prime” the marker

Pump the nib of the marker a couple of times to start the flow of ink. Lay out a piece of paper and only pump on a horizontal surface (don’t try this on the table)!

A few important tips:

Store with the nib facing upwards!

AcrylicOne markers are significantly different from No.One, BigOne and fineOne series markers. They have valves and mixing balls inside the marker.
It is therefore not recommended to store them with the nib facing downward. If this happens, acrylic pigment can collect in and clog the valve. Ensure that you store this special kind of marker in the right way.

Do not prime the marker on the table!

Pumping opens the valve inside the marker and the acrylic ink flows to the nib. For this reason, the marker should be kept as vertical as possible. We expressly recommend doing this on a table with an appropriate underlay. Pumping on an inclined or wall-mounted table can cause unwanted flows of ink from the marker’s ventilation slots.

Shake well!

Acrylic ink is made up of pigment, a binder and a solvent – water. As this can settle over time, it is important to mix these together again by shaking the marker evenly. This sets the two glass marbles in the marker and/or the refill in motion, and performs this mixing task. The marbles are only actually moving if you can hear a rattling sound. If the marker stays silent, the marbles may still be lodged in a thickened part of the acrylic paint. This means only one thing: “keep shaking the marker” until you can clearly hear the rattling sound.