Dropper caps are common in beauty products that are dispensed in smaller quantities like serums and essential oils. They're sometimes used for more medicinal purposes as well. To pull liquid into the pipette, pinch then squeeze. To push liquid out, squeeze again.
The top bulb is made from a soft rubber. The cap is made from a harder PP plastic. The pipette can be made from glass or plastic and it can be straight or curved.
Stock bulb colors are black or white. Caps can be black, white, gold, or silver. Depending on your product usage, you may want to consider having volumetric markers printed on the pipette.