Abstract: A cap capable of being secured to a chimney or flue of either air cooled or non-air cooled type and including a base, an annular collar member for insertion into a chimney or flue, an annular shaped mesh member that is supported from the base; a top supported on the annular shaped mesh member, means supported from an outer surface of the collar member below the base and forming a ledge for support of the collar member from the chimney or flue, and an over lap joint including a lower segment that extends substantially longitudinal of the collar member and a top segment that extends diagonal to the lower segment enabling compression of the diameter of the collar member.