Abstract: An upright ESFR sprinkler includes a generally tubular body, at least one frame arm, a closure assembly, an unactuated heat responsive trigger assembly and a deflector assembly with a K-factor greater than 14, and preferably 16.8. The passageway extends between inlet and outlet openings. The closure is positioned proximate the outlet so as to occlude the passageway with a Bellville seal being. An ejection spring is coupled to the closure assembly. The heat responsive trigger assembly has a Response Time Index of 40 meter1/2second1/2 (m1/2sec1/2) or less. The deflector assembly includes a nosepiece and a plate like redirecting member. The plate like redirecting member faces the outlet and is coupled to the at least one frame arm and spaced from the outlet opening. The plate shaped member includes a first generally planar portion, a conical second portion, and a third portion extending from the conical second portion.