Metal tube Rotameters are recommended for liquids or gases where process or operating conditions make all-metal construction desirable. This type of Rotameter is also useful for metering opaque fluids. These are very rugged and robust yet inexpensive for flow rate indication purposes. They can be used for opaque and turbid fluids at high operating temperature and pressures. The Flow is indicated by a pointer, which is magnetically coupled with the float that rises in a tapered tube with increase in flow.