Steel Drain Stopper / Test Plug - 4" is a heavy-duty mechanical plug used by plumbers to seal or pressure-test four-inch (100mm) drain pipes. It is primarily used for air or water tightness testing of drainage and sewer systems. 
Product Specifications
Size: 4 inches (100mm) internal diameter.
Pipe Diameter Compatibility: Fits internal pipe diameters from 94mm to 110mm.
Material: Manufactured from high-quality zinc-plated steel for corrosion resistance, with a compressible rubber sealing ring for a secure fit.
Test Point: Features a 1/2 inch BSP (British Standard Pipe) outlet port for connecting a pressure gauge, hose, or hand test pump.
Maximum Back Pressure: Rated to handle a maximum allowable back pressure of 10 psi(approximately 0.69 bar).
Operation: Tightened using a robust central wing-nut, which expands the rubber seal to create an airtight or watertight seal.