The McAlpine VP50P Ventapipe 50 Air Admittance Valve is a plumbing device that is designed to allow air to enter the drainage system, while preventing foul odors from escaping into the building. This valve features a dual fit synthetic rubber finger seal outlet, which means that it can be connected to both 3"/75mm and 4"/110mm soil pipes. This can be especially useful in situations where different pipe sizes are used in the same plumbing system. The VP50P Ventapipe 50 is manufactured by McAlpine, a well-known and respected brand in the plumbing industry.