A filter cap made of resinous material, and includes a housing with ceiling wall, a circumferential wall, an atmospheric port formed in the circumferential wall, and edges having a slanting surface. The filter cap reliably ensures installation in various devices and improves the corresponding assembly and resulting work efficiency of such devices. The filter cap can house an air filter in a predetermined location and protect an associated air passageway from water and foreign deposits such as, for example, mud