A residential flat plate concealed sprinkler comprising: a body having an inner surface defining a passageway for carrying a fluid, the passageway including an inlet and an outlet spaced apart along the longitudinal axis (A-A) and defining a K-factor of about 5; a closure assembly adjacent the outlet to occlude the outlet; thermally responsive support means for maintaining the closure assembly adjacent the outlet; a deflector assembly having a first position distal to the outlet and a second position distal to the first position, the deflector assembly including a plate; a pair of telescopic guide members each having a proximal end and a distal end, the proximal end being coupled to the body, the distal end of the guide members being coupled to the plate; and a thermally responsive trigger assembly that maintains the closure assembly adjacent the outlet, wherein, the deflector assembly plate has a substantially oval outer perimeter having a first plate axis and a second plate axis, the distance between portions of the substantially oval outer perimeter along the first axis being greater than the distance between portions of the substantially oval outer perimeter along the second axis, a plurality of diametrically opposed pairs of slots disposed along the substantially oval outer perimeter, the plurality of slots disposed on either side of the first plate axis and the second plate axis further defining a first slot group having a first slot length, and at least a second slot group having a second slot length smaller than the first slot length; and a projection coupled to the plate in each of the first position distal to the outlet and the second position distal to the first position; the distal end of the guide members being coupled to the plate along the first plate axis between the pair of slots and adjacent an edge that forms each of the slot of each of the pair of slots; and the trigger assembly has a fusible link assembly spaced from the projection when the deflector assembly is in the first position, and wherein the deflector assembly distributes a flow of fluid over a protection area ranging from about 13.38m 2 (about 144 square feet) to about 37.16m 2 (about 400 square feet), the fluid distribution having a density of at least 2.037 litres per minute per m 2 (0.05 gallons per minute per square foot (0.05 gpm/ft 2)) so as to define a range of minimum operating pressures ranging from about 48.26kPa (seven pounds per square inch) to about 117.21kPa (seventeen pounds per square inch (7-17 psi.)) and a range of minimum operating fluid flows ranging from about 49.21L/m (thirteen gallons per minute) to about 75.71L/m (twenty gallons per minute (13-20 gpm)). a body having an inner surface defining a passageway for carrying a fluid, the passageway including an inlet and an outlet spaced apart along the longitudinal axis (A-A) and defining a K-factor of about 5; a closure assembly adjacent the outlet to occlude the outlet; thermally responsive support means for maintaining the closure assembly adjacent the outlet; a deflector assembly having a first position distal to the outlet and a second position distal to the first position, the deflector assembly including a plate; a pair of telescopic guide members each having a proximal end and a distal end, the proximal end being coupled to the body, the distal end of the guide members being coupled to the plate; and a thermally responsive trigger assembly that maintains the closure assembly adjacent the outlet, wherein, the deflector assembly plate has a substantially oval outer perimeter having a first plate axis and a second plate axis, the distance between portions of the substantially oval outer perimeter along the first axis being greater than the distance between portions of the substantially oval outer perimeter along the second axis, a plurality of diametrically opposed pairs of slots disposed along the substantially oval outer perimeter, the plurality of slots disposed on either side of the first plate axis and the second plate axis further defining a first slot group having a first slot length, and at least a second slot group having a second slot length smaller than the first slot length; and a projection coupled to the plate in each of the first position distal to the outlet and the second position distal to the first position; the distal end of the guide members being coupled to the plate along the first plate axis between the pair of slots and adjacent an edge that forms each of the slot of each of the pair of slots; and the trigger assembly has a fusible link assembly spaced from the projection when the deflector assembly is in the first position, and wherein the deflector assembly distributes a flow of fluid over a protection area ranging from about 13.38m 2 (about 144 square feet) to about 37.16m 2 (about 400 square feet), the fluid distribution having a density of at least 2.037 litres per minute per m 2 (0.05 gallons per minute per square foot (0.05 gpm/ft 2)) so as to define a range of minimum operating pressures ranging from about 48.26kPa (seven pounds per square inch) to about 117.21kPa (seventeen pounds per square inch (7-17 psi.)) and a range of minimum operating fluid flows ranging from about 49.21L/m (thirteen gallons per minute) to about 75.71L/m (twenty gallons per minute (13-20 gpm)).