Wall Mixer FIO Series refers to a specific line or series of wall-mounted mixers produced by a brand or manufacturer called FIO. A wall mixer is a plumbing fixture that combines hot and cold-water streams to provide a mixed flow of water. It is typically installed on the wall and is used to control the water temperature and flow rate for various purposes, such as bathing or showering. Wall mixers usually feature a handle or lever that allows one to adjust the water temperature by controlling the proportion of hot and cold water.