A shower mixer is a plumbing fixture that controls the flow and temperature of water in a shower. It is designed to combine hot and cold water to provide the desired water temperature for showering. A shower mixer typically consists of a valve or control mechanism that allows the user to adjust the water flow and temperature by turning a handle or lever. 

The valve is connected to both the hot and cold water supply lines, and by adjusting the handle or lever, the user can blend the two water streams to achieve the desired temperature. Some shower mixers may also include additional features such as thermostatic controls, which help maintain a consistent water temperature even if there are fluctuations in the hot or cold water supply. Shower mixers come in various styles and designs to suit different bathroom aesthetics, and they can be wall-mounted or integrated into a shower system. They are an essential component of a functional and comfortable shower experience, providing control and convenience for users to enjoy their preferred water temperature while showering.