If you teach CPR with masks instead of manikin face shields, this training valve offers big savings over using standard one-way valves. This valve will fit most CPR face masks. The 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”. This training valve will fit on the inside opening of adult masks and fits over the infant mask opening. This valve is great for training purposes only.