a double balloon with two chambers and with a narrowed connecting area the balloon 6 is preferably stretched out when the fixation arms 40 are deployed as can be seen in fig8 the balloon is preferably made of pet polycarbonate polyvinyl chloride pp or silicone the balloon sheath can also be arranged inside the fixation arms 40 and thus inside the fixation unit 4 fig9 and 10 show another variant of a closure body this closure body is a circular membrane 7 for example of pet or dacron u00ae the closure body is connected to the fixation arms 40 of the distal or proximal end in this example both the distal and also the proximal fixation arms 40 each have a membrane 7 however it is also possible for a membrane 7 to be present only on one side the membrane 7 is preferably in each case located on that side of the fixation arms 40 directed toward the corresponding endpiece 20 30 the membrane 7 can be sewn onto the fixation arms 40 adhesively bonded to them or connected to them in some other way as can be seen in fig1 these membranes 7 are stretched out by means of the fixation arms 40 the membranes can also be arranged inside the fixation unit 4 that is to say on the other side of the fixation arms 40 the various closure bodies mentioned can also be combined with one another in the same occluder fig1 shows another illustrative embodiment of the occluder according to the invention it has basically the same structure as the occluders described above and it can.