The pipette filler
A pipette filler is used for pipetting and is made of rubber (usually red or green).
A pipette filler is always used with a glass pipette, either graduated or volumetric.
It is important not to push the pipette too deeply into the pipette filler, otherwise it will not work well. Do this carefully to avoid breaking the glass pipette and injuring yourself.
check the sheet How is pipetting performed?