In a closed system there must be a barrier (aka backflow protector) to prevent milk from entering into pump tubing.

Just like breast pumps manufactured by diverse brand makers have various styles and appearance, the barriers also have different looks. The diaphragm in Maymom backflow protector is circular and rather flat and is often called as a membrane.

From other makers like Ameda and Philips Avent, the diaphragm can be cylindrical and looks like a container. It isolates pump and tubing from the space where breast milk is expressed, flows and is collected, protecting the milk from contamination.

To maintain the performance of your pump, replacing the worn or deteriorated part is highly recommended.

Here is the replacement diaphragms made by Maymom and compatible with OEM parts.