with reference to fig1 - 4 , these show a ventilation element 1 comprising a rigid body 2 , made of plastic or sintered material and having a cylindrical part 3 closed at a first end 4 by a closure part 5 and open at a second end 7 . the part 5 is preferably integral with the cylindrical part 3 . an internal cylindrical portion 10 projects from an inner side 8 ( with respect to the body 2 ) of said part 5 , with which it is integral , and extends as far as the second end 7 of the body 2 . this internal portion 10 hence forms a part of the body 2 , i . e . is in one piece with it . the internal portion 10 is coaxial with the cylindrical part or outer wall 3 of the body 2 , between these there being a recess or interspace 12 . the portion 10 and said wall 3 are connected together by ribs 11 k which stiffen the body 2 and prevent its deformation with time due to thermal cycles , vibrations or atmospheric agents . as will be described , this recess 12 of the body 2 is in communication with a compartment 13 present between the closure part 5 and a first end 14 of a cylindrical member 15 inserted coaxially into the internal cylindrical portion 10 of the body 2 and retained within this latter by interference with said portion . said member 15 is of yieldable material , such as natural or synthetic rubber or equivalent material , and comprises a second end 17 projecting from the body 2 . the first end 14 of the member 15 is located in a position corresponding with but spaced from the closure part 5 of the body 2 , the aforesaid compartment 13 hence being formed between this part and said end . to ensure the spaced positioning of the member 15 from said closure part 5 , shoulders 21 project from the inner side 8 of this latter , on which the first end 14 of the member 15 rests . the shoulders 21 are of arched shape and contact the member 15 on the inside of the cylindrical portion 10 of the body 2 . as stated , the interspace or recess 12 communicates with the compartment 13 via slots 22 provided in said portion 10 , advantageously to the front of the shoulders 21 . these slots , preferably having sharp edges , cooperate with the cylindrical member 15 and contribute to maintaining this member coupled to the portion 10 . this takes place in particular by virtue of the further deformation of the member 15 when connected to the housing on which the element 1 is mounted . this connection is achieved by mounting the member 15 on a male element of said housing ; this causes said deformation which , added to the thrust which the member 15 generates on the portion 10 on mounting the element 1 , causes said member to cooperate in strict adherence with the slots 22 to hence lock it within the rigid body 2 . this fact means that on separating the element 1 from said housing , the member 15 becomes reliably detached from this latter as it forms essentially one piece with the rigid body 2 . at the first end 14 , the member 15 supports a membrane of known hydrophobic material 25 , while at the second end 17 of this member the element 1 is coupled to the housing which is to be ventilated . the membrane 25 can be flat or have a different shape , with its surface continuous or presenting a succession of crests and depressions , for example as a concave surface ( for example conical with its vertex facing the side 8 ) or convex . as visible in fig9 , a variant of the invention is shown presenting a conical membrane 25 . in this variant , the closure part 5 can be flat as in the previous figures or have a shape which follows the membrane profile as shown in fig9 . for ventilation , the air of the housing with which the element 1 is associated passes through the conduit 30 of the tubular member 15 , passes through the membrane 25 and from there into the compartment 13 . the air passes through the slot 22 into the interspace 12 and emerges from the body 2 through its second end 7 . by virtue of he fact that the recess or interspace 12 is defined by two rigid parts ( the wall 3 and the portion 10 ), it is non - deformable and ensures constancy in the ventilation air flow . this enables the ventilation air flow rate to be optimized by suitable dimensioning of the interspace 12 of the body 2 and of the slots 22 , said flow rate hence not depending on components of variable dimensions as for example is the case of known solutions in which ventilation takes place between a rigid and a yieldable body , for example of rubber . in the case of the present invention , as the flow always takes place between rigid parts ( the wall 3 and the portion 10 ), it can be calculated precisely and be guaranteed by suitable design of the rigid body 2 . in addition , this ventilation is achieved precisely and only via the body 2 , the member 15 being used only for supporting the membrane 25 and for securing the element 1 to the housing to be ventilated . the member 15 supporting the membrane 25 is moreover well protected by the body 2 and by its two coaxial parts , the wall 3 and the portion 10 . this protection is to be considered valid both against impacts to which the member 15 could be subjected and against external agents , such as variation in the temperature of the air surrounding the element 1 , which could worsen the performance of said element with time by limiting its deformation or “ relaxation ”. in addition , the element 1 makes little use of components of yieldable material , which have a cost exceeding that of rigid components , for example of plastic . the cost is hence lower than known solutions with lesser production times than these latter . moreover , the shape of the body 2 with the cylindrical portion 10 and of the member 15 , also cylindrical , facilitates their manipulation during assembly of the element 1 , achieved by automatic machines . this is because of the simplicity of the geometrical shape of said body 2 and member 15 which are easy to handle and couple together . finally , the member 25 is inserted into the portion 10 and contacts the entire surface of this latter . this maximizes the seal of the assembly with time , without projections or other coupling members being required on at least one from said portion and said member . in fig5 - 8 , in which parts corresponding to those of the already described figures are indicated by the same reference numerals , the element 1 comprises apertures 40 provided in proximity to or at the closure part 5 of the body 2 . these apertures 40 are through apertures and communicate with the compartment 13 ; within this latter the shoulders 21 on which the member 15 rests are present in front of said apertures . the function of these shoulders , as also in the embodiment of fig1 - 4 ( but with greater emphasis in the embodiment under examination ), is to disperse into the compartment 13 any water droplets which pass through the apertures 40 ( or the slots 22 of the previously described embodiment ) and prevent their impact against the membrane 25 associated with the member 15 in proximity to the closure part 5 . the cylindrical portion 10 projects from said part 5 but , in contrast to the embodiment of fig1 - 4 , does not extend as far as the second end 7 of the body 2 , but terminates within this latter . the extension of said portion 10 , however , is such that it couples by interference to the member 15 to hence retain it secured to the body 2 . to improve this retention , shoulders or uprights 43 extend from the portion 10 in one piece with this portion and with the wall 3 of the body 2 , having a free wall 44 cooperating by interference with the member 15 and contributing to retaining this latter in the body 2 . in the embodiment of fig5 - 8 , the ventilation of the housing to which the element 1 is connected takes place by a flow which passes through the member 15 , through the compartment 13 and emerges from the body 2 through the apertures 40 . the aforedescribed solution also presents at least part of the advantages already indicated with reference to the embodiment of fig1 - 4 . various embodiments of the invention have been described . others are however available in the light of the aforegoing description and are to be considered as falling within the scope of the following claims .