A filter which can be attached to a connection flange, wherein the filter has an exchangeable filter insert having a hollow cylindrical filter material body enclosed on its faces by two end plates, wherein the filter has a cup-shaped housing, which can be sealed in the assembled state on the free edge against a sealing surface of the connection flange by means of a circumferential seal, and wherein the seal is arranged on the outside circumference of a circumferential seal carrier forming a part of the filter insert. The filter seal is a sealing ring having a rectangular cross-section in an unloaded state, radial contours being arranged on the outer circumference of the seal carrier, and, during assembly of the housing, the seal can be pressed into the engagement contours and is permanently malleable, undergoing axial shortening and radial expansion on the inner circumference thereof.