Monument testing plugs are durable, quality flexible drain plug for the pluging of drains and pipes. This plug is easy to use and are avaliable in 3 and 4-inch versions. These plugs are easy to use just place in the pipe end that is being repaired or replaced and simply turn the wing nut knob, this will depress the rubber cone, this will make it expand to seal pipe or tube end with a water tight seal. Used for blocking off drain pipes. Fitted with removable top caps and rubber rings. Monument 1378Z Drain Testing Plug. Size: 100 mm (4 in). Capable of sealing against pressures of up to 1.97 bar / 29 psi.