Filter housing with a sealing surface and a central standpipe for pushing a filter insert according to claim 2 with its through hole comprising end plate first onto the standpipe, wherein (a) a locking ring is guided on the standpipe in an axially displaceable manner, (b) the locking ring is preloaded with a force acting in the extension direction pointing towards the free end of the standpipe, (c) the locking ring has an extension position, in which it is blocked by a locking device against pushing-in, (d) the locking device i) can be actuated in an unlocking direction and ii) is arranged such that by pushing-on the filter insert according to claim 2, the locking device is actuated in the unlocking direction by the unlocking means which is guided by the filter insert, (e) the locking device and the locking ring are arranged to each other in such a manner that an actuation of the unlocking device in unlocking direction enables pushing-in of the locking ring and the filter insert, characterized in that (f) with the locking ring in extension position and with the filter insert according to claim 2 axially abutting the locking ring, the sealing of the filter insert according to claim 2 being provided at the end plate of the filter insert, is axially remote in the extension direction from the associated sealing surface of the filter housing and is held in a non-sealing position remote from the sealing surface by the locking device, and (g) with the filter insert according to claim 2 being in pushed-in position, with unlocked locking device, the sealing surface and the sealing of the filter insert according to claim 2 cooperate in a sealing manner, wherein they separate a raw side and a clean side of a filter, and (h) positioning guidance means are provided on the outer circumference of the standpipe, wherein the positioning guidance means are formed such that the positioning guidance means cooperate with the guiding means arranged at the inner circumference of the filter insert according to claim 2. (a) a locking ring is guided on the standpipe in an axially displaceable manner, (b) the locking ring is preloaded with a force acting in the extension direction pointing towards the free end of the standpipe, (c) the locking ring has an extension position, in which it is blocked by a locking device against pushing-in, (d) the locking device i) can be actuated in an unlocking direction and ii) is arranged such that by pushing-on the filter insert according to claim 2, the locking device is actuated in the unlocking direction by the unlocking means which is guided by the filter insert, i) can be actuated in an unlocking direction and ii) is arranged such that by pushing-on the filter insert according to claim 2, the locking device is actuated in the unlocking direction by the unlocking means which is guided by the filter insert, (e) the locking device and the locking ring are arranged to each other in such a manner that an actuation of the unlocking device in unlocking direction enables pushing-in of the locking ring and the filter insert, characterized in that (f) with the locking ring in extension position and with the filter insert according to claim 2 axially abutting the locking ring, the sealing of the filter insert according to claim 2 being provided at the end plate of the filter insert, is axially remote in the extension direction from the associated sealing surface of the filter housing and is held in a non-sealing position remote from the sealing surface by the locking device, and (g) with the filter insert according to claim 2 being in pushed-in position, with unlocked locking device, the sealing surface and the sealing of the filter insert according to claim 2 cooperate in a sealing manner, wherein they separate a raw side and a clean side of a filter, and (h) positioning guidance means are provided on the outer circumference of the standpipe, wherein the positioning guidance means are formed such that the positioning guidance means cooperate with the guiding means arranged at the inner circumference of the filter insert according to claim 2.