The bulb is made out of rubber and controls the dosage. So, simply put: The bigger the bulb, the bigger the dosage. The pipette bulb comes in different sizes and indicates how many millilitres can be sucked in by squeezing it. And that's what the number stands for 0.4, 0.7, and 1.0 refers to the amount of ml.
The difference between TPE and NBR? TPE stands for thermoplastic elastomer and is the standard bulb most commonly used for alcohol-based and low acidity level products that can't damage the rubber bulb. NBR, nitrile rubber bulb, is a specialized bulb for oil-based and high acidity liquids.
If you wonder what acidity level is high or low, the answer is not as straightforward as it may seem. A general rule of thumb is: The purer the product, and the fewer oils or alcohols are added, the higher the acidity level. But every product is different. We advise you to test your product with both bulbs first.
Hole cap (the body)
There are Type III and child-resistant (CR) tamper-evident caps. Tamper-evident means that they have a plastic ring at the bottom of the cap that breaks after the first time opening. They act as quality control for the customer. An intact ring means the bottle has not been opened before.
The child-resistant cap needs to be pushed down and turned to open. When it comes to deciding which cap is best for your natural product, the main question is if the content needs to be protected from children. CBD products, for example, often need CR closures.