Abstract: A flashing system configured to reduce moisture intrusion at an opening extending through an exterior treatment of a building structure. The flashing system includes at least one flashing piece having a main flashing portion and a sealing flange. The main flashing portion is configured to extend outward a distance from a periphery of the opening of the building structure to provide an effective moisture barrier and configured to be positioned against a wall having the opening defined therein. The sealing flange of the at least one flashing piece includes a top sealing flange, a bottom sealing flange, a first side sealing flange and a second side sealing flange each configured to extend outward from the main flashing portion and is configured to be positioned adjacent a peripheral-opening-structure at a respective top periphery, bottom periphery, first side periphery and second side periphery of the opening. The flashing system also includes a first top tab and a second top tab.