Aluminum is economical and good for general use with noncorrosive gases and liquids. Brass is economical and good for use with water. Stainless steel withstands higher temperature and pressure and features excellent chemical compatibility. Valved meters have valves mounted at the bottom/inlet, typically used for positive pressure with liquids and gases. The valve can be reconfigured to mount at the top/outlet, often for vacuum applications. All correlated flowmeters come with data sheets for water and air at standard temperature and pressure (STP).