This wiper seal is designed to fit inside the neck of a GL18 (DIN18) glass bottle & our Mallaig range of bottles with code MCR (20/410). It is for use with dropper pipettes with a pipette tube diameter of circa 7.25mm. Its purpose is to wipe off any excess liquid adhering to the pipette as it is drawn out of the bottle. Without this insert, when the user re-inserts the pipette back into the bottle, the pipette stem will rub against the top of the bottle neck and some of the excess product will be deposited, often spreading and running down the threads as the cap is re-applied. If this is an oily substance, the effect is a slippery thread, leading to cap back-off and leakage issues. If it is a product that may tend to dry out, this results in unsightly residue forming on the outside of the bottle neck, which can damage your brand image.