For nozzles and pump heads, the external pump, that is, the spring in the center of the nozzle/pump head, is externally visible, generally placed above the pump core, and the assembly is directly connected to the nozzle/pump head cap. The advantage of the external pump is that it does not directly contact the liquid in the bottle, which is not only environmentally friendly and hygienic but also 100% avoids rust on individual springs, which affects the quality of the products in the bottle. Most springs are treated. In addition, the force of the external pump is larger than that of the built-in pump, so the general pump head uses more external pumps, which are suitable for more viscous liquids such as emulsion stock solution.
    In contrast to the external pump, the built-in pump, that is, the spring in the center of the nozzle/pump head, is invisible and is generally located in the middle of the pump body. The internal spring can directly contact the liquid, and the pressure channel is slightly smaller than that of the external pump. Some are generally used in health care products, essential oils, perfumes, and skin care waters, which are closer to water.