A double cup used in a nest box to hold water on one side and feed on the other. Also very handy when you have a bird in sick bay. Screw the bracket to the wall. Each cup may be removed individually. The cups come with removable no waste, no spill lids. All plastic construction, total length is 7 1/2 in. Each side holds 4 oz. of liquid or equivalent of food Double Nest Box Cup