The VK558 is a K5.6 Quick Response Upright Intermediate Level In-Rack Sprinkler with a 1/2" NPT thread size and standard orifice size. 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.