Standard replacement inflation bulb for a 2-tube sphygmomanometer. The aperture of the rubber bulb is about 1/4 to 5/16 inch, with metal intake value. It does not include the air-release valve that fits into the open hole on the bulb. If you have noticed a leak in your old bulb you can easily replace it with this dark blue soft latex-free PVC material. The advantage of this material is it won't decompose on you as the years go by the way rubber will. Be sure to check your inflation system as those may develop leaks over time as well.