Flat Tile VentsModel LOR9-4, Lo-OmniRidge® Low profile 4' shingle over ridge vent. 44 square inches of Net Free Area per 4' piece.Model LOR9-4, Lo-OmniRidge® Low profile 4' shingle over ridge vent. 44 square inches of Net Free Area per 4' piece.Model LOR9-4, Lo-OmniRidge® - Installation 4' tile exhaust vent, 9 square inches of Net Free Area per linear foot of installed vent.Model LOR9-4, Lo-OmniRidge® - Installation 4' tile exhaust vent, 9 square inches of Net Free Area per linear foot of installed vent.