fig1 to 10 show schematically illustrative embodiments of an assembly according to aspects of the invention comprising a compensating reservoir 1 and a master cylinder 2 for a hydraulic motor vehicle brake system , the construction and operation of which are fundamentally known . after the mounting of the compensating reservoir 1 on the master cylinder 2 , connection stubs ( not shown ) of said reservoir are accommodated in corresponding connection openings of the master cylinder 2 and connect pressure medium chambers of the compensating reservoir 1 to pressure spaces of the master cylinder 2 in a known manner . for releasable connection to the master cylinder 2 , the compensating reservoir 1 has two fastening lugs 3 , 4 , each with an opening 5 , 6 . after the mounting of the compensating reservoir 1 on the master cylinder 2 , these openings 5 , 6 are in alignment with an opening 7 in the master cylinder 2 . for fastening , a fastening pin 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 36 made of plastic is provided , which extends through the aligned openings 5 , 6 , 7 . in the region of a master cylinder lug 8 , the opening 7 in the master cylinder 2 is provided as a through hole , which extends between reservoir connections ( not shown ) of the master cylinder 2 . common to all the illustrative embodiments described below is the fact that the fastening pin 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 36 provided is made from a harder plastic than the compensating reservoir 1 . it is thereby possible to ensure that the fastening pin 9 to 16 is not damaged during its installation and during its possible removal . for example , the fastening pin 9 to 16 , 36 provided can be made from glass - reinforced polyamide , although other plastics materials can also be used within the scope of the invention . in order to simplify the installation of the fastening pin 9 to 16 and to make it possible without the aid of tools and to obtain an assembly which is optimized in terms of weight , the fastening pin 9 to 16 , 36 provided in the respective illustrative embodiment is made of plastic and interacts positively or nonpositively with at least one of the openings 5 , 6 in the fastening lugs 3 , 4 and with the fastening lugs 3 , 4 . to simplify positioning during installation , the fastening pin 9 to 16 , 36 has a head flange 18 , 38 at a first end 17 , 37 for the purpose of resting against one of the fastening lugs 3 , 4 . it is particularly advantageous here if , where possible , the fastening pin 9 to 16 , 36 and the fastening lugs 3 , 4 are designed in such a way that installation can take place from both sides , i . e . from both fastening lugs 3 , 4 . fig1 to 6 show five illustrative embodiments in which the fastening pin 9 to 13 has one or more latching elements , which interacts positively with at least one of the openings 5 , 6 in the fastening lugs 3 , 4 . the latching elements can be provided in a simple manner during the production of the fastening pin 9 to 13 , thereby making it possible to omit additional machining . fig1 shows a detail of an assembly according to aspects of the invention of a first illustrative embodiment . as can be seen , the openings 5 , 6 in the fastening lugs 3 , 4 each have a recess 19 , 20 on an inner side , with the result that the openings 5 , 6 are of stepped design , with a small diameter on an outer side and a large diameter on the inner side . the fastening pin 9 has a plurality of latching noses 21 , which engage in the recess 19 after the installation thereof . the latching noses 21 are dimensioned in such a way that they can be deformed during installation through the opening 5 . since both fastening lugs 3 and 4 each have a stepped opening 5 , 6 with the same diameters , installation from both sides is possible . fig2 to 4 show illustrative embodiments in which the fastening pins 10 to 12 have , at the second ends 27 thereof , one or more resilient latching arms 22 to 24 , which can engage on the fastening lug 3 , 4 after the installation of the fastening pins 10 to 12 . fig2 shows a second embodiment . the fastening pin 10 has two latching arms 22 , which are advantageously pressed together resiliently during installation and during removal . for this purpose , the latching arms 22 are arranged substantially in a u shape , and the latching arms 22 each have two guide bevels 25 , 26 . as is apparent from fig2 , the guide bevels 25 allow the latching arms 22 to be pressed together during the installation of the fastening pin 10 , and the guide bevels 26 allow them to be pressed together during the removal thereof . as can be seen from fig3 and 4 , the latching arms 23 , 24 of the third and fourth illustrative embodiments are dimensioned in such a way that the fastening pin 11 , 12 does not have a larger diameter in the region of the latching arms 23 , 24 if the latching arms 23 , 24 are pressed together during installation . owing to the design of the latching arms 23 , 24 , the fastening pins 11 , 12 cannot be removed . fig5 and 6 show a fifth illustrative embodiment , the fastening pin 13 of which has resilient spiral latching elements 28 at its second end 27 , with a diameter of the end 27 being smaller than a diameter of the opening 7 in the master cylinder 2 in order to ensure simple installation of the fastening pin 13 . in order to prevent rattling of the fastening pins 9 to 13 of the illustrative embodiments under consideration in the opening 7 in the master cylinder 2 , provision can be made in these for the fastening pins 9 to 13 to have means for wedging in the opening 7 in a central section 29 . these means can be axially oriented projections 30 , for example , as illustrated in fig2 . as an alternative , the fastening pins 9 to 13 can be provided with a convexity , i . e . can be arched , in the central section 29 . in this case , an axially oriented slot allows simple installation through the opening 7 in the master cylinder 2 . a sixth illustrative embodiment in accordance with fig7 provides a nonpositive connection between the fastening pin 14 and a fastening lug 3 , 4 , which can be achieved in a simple manner if the fastening pin 14 has , at the second end 27 thereof , a thread - or fir tree - shaped profile 31 which can be wedged in the opening 5 , 6 . according to fig8 and 9 , which show a seventh and eighth illustrative embodiment , the fastening pin 15 , 16 can have , at the second end 27 thereof , a thread - or fir tree - shaped profile 32 , 33 which interacts with a complementary profile 34 , 35 in the opening 6 in the fastening lug 4 . a ninth illustrative embodiment is shown in fig1 . the fastening pin 36 likewise has , at a first end 37 , a head flange 38 for the purpose of resting against one of the fastening lugs 3 , 4 . in contrast to the illustrative embodiments described above , however , the head flange 38 has two resilient projections 39 , which engage positively in recesses 40 , 41 on an outer side of the fastening lugs 3 , 4 after installation . since the recesses 40 , 41 are provided on both fastening lugs 3 , 4 , installation can take place from both sides . installation from both sides is advantageously possible if the openings 5 , 6 have an identical diameter . for this purpose , the fastening pin 10 illustrated in fig2 has a uniform diameter in the region of the openings 5 , 6 , for example . stepping of the fastening pin 10 , 11 , 12 , 14 , 15 , 16 after the head flange 18 , as illustrated , is thus not absolutely essential .