The VK553 is a K11.2 Standard Response ELO Upright Intermediate Level In-Rack Sprinkler with a 3/4" NPT thread size and extra large orifice (ELO). Intermediate level in-rack sprinklers are pre-assembled with the water shields factory installed. They are available with or without sprinkler guards. Viking Water Shields protect sprinkler heat-sensing elements from water spray discharging from sprinklers located at a higher elevation.