Model No. 20357;Provides complete protection against positive and negative pressures in the system;Replaces extensive vent piping saving material and installation costs;Provides greater freedom of design for engineers, architects and design professionals;Eliminates leak prone roof penetrations. No roof penetrations are required no matter how tall the building;Reduces the need for fire stopping devices preventing the chimney effect in the pipes, reducing the risk of fire spreading upwards between floors;Can be retrofitted into an existing drainage system to solve positive pressure problems;Prevents propagation of oderous sewer gases;Requires no maintenance, as all Studor products are non-mechanical devices;10 year warranty for replacement of defective devices;Easy to install, does not require high skilled labor or special training