This virtually indestructible cover (slotted for a horn/ strobe or speaker/ strobe unit) is molded of clear, thick, UV-stabilized polycarbonate material to help stop vandalism and accidental damage to surface mount strobe/ horn/ speaker units. The Stopper Dome is backed by a lifetime guarantee against breakage of the polycarbonate in normal use. Slots in the cover allow the horn to be heard and the open backbox will accommodate exposed conduit.