Viking Early Suppression Fast Response (ESFR) Upright Sprinkler VK520 is a fast response fusible element type sprinkler designed for early fire suppression.  With a 14.0 (202 metric) nominal K-Factor and special deflector, this sprinkler produces large, high-momentum water droplets in a hemispheric pattern below the deflector. This permits penetration of the fire plume and direct wetting of the burning fuel surface while cooling the atmosphere early in the development of a high-challenge fire.