The SF flowmeters are devices for the supply of medical gases particularly suitable in respiratory therapy. They are made of anodized aluminum body, and they are available with one or more graduated tubes and a built-in dosage unit. The inlet connections are at the bottom of the unit and arranged to be connected to the hospitals centralized gas plants or to cylinders complete with pressure regulators. For veterinary use, an anesthesia evaporator can be connected at the outlet of the dosage unit.