The MF-3 will fit into all 4 inches (110mm) drain pipes, clay, plastic, and cast. The MF-3 one-way valve will stop the light penetration that attracts rodents and snakes which look for the light source. The product will not fall down the pipe due to a gasket which opens the rubber. The MF-3 can be fitted in seconds and there is no need for a plumber or tradesperson as this can be fitted by anyone. The MF-3 can also act as a solid matter backflow preventer valve.