Standard cast aluminum ventilated well caps, with conduit opening, for use on steel or plastic casiing. Stainless steel set screws. The well cap is the cover on top of the well casing that sticks out of the ground. The well cap is vented so that the pressure difference between the inside and outside of the well casing is equalized when water is pumped from the well. The well cap serves many purposes. However, the cap's main function is to keep contaminants out of the water supply. It is the first line of protection against runoff of pesticides and herbicides, soil erosion, and elements from the street, which constitutes the majority of ground water contamination. Well caps also keep out insects which can increase bacteria levels in the well.