19 a coupling section is formed which comprises several for example three projections 20 a connecting element 21 can be screwed into the second counter thread 17 and will be described in more detail in the following with reference to fig3 and 4 in this context fig3 shows a perspective view of the connecting element 21 fig4 shows a perspective partial view of a kit comprising the filter device 1 of fig1 as well as the connecting element 21 the connecting element 21 has a tubular section 22 which supports at one end an outer thread 23 on one end of the tubular section 22 projections 24 are provided that form a coupling section the projections 24 for example three such projections extend parallel to an axis of rotation 25 of the thread 23 moreover the projections 24 are distributed about the axis of rotation 25 preferably uniformly and extend according to the present embodiment away from the thread 23 at the other end the tubular section 22 has a connecting socket 26 for connecting a hose not illustrated the connecting element 21 comprises moreover a profiled ring 27 which is arranged coaxial to the tubular section 22 the ring 27 is connected by means of a circumferential web 31 fixedly to the tubular section 22 the ring 27 is arranged approximately centrally between both ends of the tubular section 22 in place of the ring 27 another type of grip can be used also the profiled ring 27 can be gripped easily with one hand in order to screw in the thread.