Use the Practi-Valve Training Valve from WNL to teach your students proper rescue breathing. This valve is compatible with CPR face masks from most manufacturers. The training valve fits into all adult WNL mask openings and it fits over the infant mask openings. This single-use valve is only intended for training. The Practi-VALVE Training Valve is 2 3/8" in height and has a fitting with an outside diameter of 7/8" and an inside diameter of 5/8". One box contains 10 training valves.