the fluid product dispenser according to the invention comprises essentially three components , namely a bellows 1 , actuation means 2 and a body or casing 3 . the bellows 1 is a single piece part , for example made from a deformable flexible material such as an elastomer or an elastomer thermoplastic . it has good deformability properties in specific areas . the bellows 1 comprises a bottom wall 11 that is almost rigid . this bottom wall 11 may be perfectly plane , but it may also be convex as shown in fig3 . fig3 shows that the bottom wall 11 forms a sort of dome or inverted dish that projects upwards . the bottom wall 11 around its external periphery defines at least one displacement flange 13 that is almost rigid . the figures show three flanges 13 . bellows 1 also forms an attachment collar 15 that is also almost rigid . for example , this attachment collar 15 may define a leak tight click fit housing 16 that will cooperate with a complementary device as can be seen below . the bellows 1 also comprises a deformable wall 14 that connects the attachment collar 15 to the bottom wall 11 . for example , the wall 14 may be made deformable by the wall being thinner than the bottom wall 11 or the attachment collar 15 . thus , the wall 11 can be moved closer to the attachment collar 15 in translation by deformation of the wall 14 . more precisely , it can be seen in figures that the deformable wall 14 forms a fold that will be accentuated if pressure is exerted tending to bring the collar 15 closer to the flanges 13 . this deformable wall 14 is the wall that justifies the name of the part , since this is the part that performs the bellows function . obviously , other means of making a deformable part could be imagined . for example , the bellows 1 could be replaced by a flexible pouch fixed on a pouch support performing the function of the attachment collar 15 . the bottom wall 11 may be replaced by a plate on which the flexible pouch is supported . the displacement flanges 13 may be formed by the periphery of the plate supporting the flexible pouch . other embodiments , such as a piston - follower that can be moved in a sliding cylinder , could also be imagined . in the embodiment shown in figures , the actuation means 2 comprise a bushing threaded on the inside 20 to form one or several internal threads 21 . as can be seen in fig3 the displacement flanges 13 of the bellows are engaged by threading with these internal threads 21 . below the threaded bushing 20 , the actuation means define an actuation and gripping element 23 that the user can grip to rotate the actuation means . optionally , the actuation means 2 form a bottom 22 that will advantageously act as a bottom for the dispenser . a continuous strip or several segments of projecting strip 24 will be formed on the outer wall of the threaded bushing 20 , extending over some or all of the periphery of the bushing 20 . it is easy to see that rotation of the actuation means 2 , while the bellows 1 is fixed , will cause displacement on the flanges 13 inside the threaded bushing 20 . the body 3 of the dispenser forms a sort of outer casing that contributes largely to the aesthetic appearance of the dispenser . the body 3 comprises a peripheral skirt 33 inside which the bushing 20 of the actuation means 2 are arranged . in the embodiment shown in figures , the skirt 33 is formed on the inside with an annular housing 34 which contains the segments of the projecting strip 24 formed on the outside of the threaded bushing 20 . the segments of the strip 24 are engaged in the housing 34 to prevent the bushing 20 from rotating in the skirt 33 . thus , actuation means 2 can rotate freely within the skirt 33 but cannot come free of it . rotation takes place freely , since the segments of the strip 24 and the housing 34 are perfectly circular and are not spiral . above the skirt 33 , the body 3 forms a tray 31 in which a hole is formed that acts as the distribution orifice 32 for the dispenser . a connection sleeve 35 extends under the tray 31 around the distribution orifice 32 . this connection sleeve has an attachment profile that engages with the leak tight attachment collar 15 of the bellows 1 . thus , the bellows 1 is fixed to the body 3 , and is not free to rotate independently of it . consequently , the assembly consisting of the bellows 1 and the body 3 form a reservoir 12 with a variable volume , given that the mobile wall 11 can move in the direction of the tray 31 by deformation of the wall 14 . this is exactly what happens when the actuation means 2 are rotated while keeping the body 3 motionless . for example , the user can grip the body 3 with his left hand and use his right hand to rotate the actuation means 2 , gripping them at the actuation and gripping element 23 . the effect is to lift the displacement flanges 13 in the internal threads of the bushing 20 . the mobile wall 11 then moves up towards the tray 31 to reduce the useful volume of the reservoir 12 . the fluid product stored inside the reservoir 12 is then forced through the distribution orifice 32 so that the user can collect it on the tray 31 . in this case , the reservoir 12 is formed by assembling the bellows 1 and the body 3 . however , it would be possible to imagine other embodiments in which the reservoir 12 is formed from a single piece , for example a flexible pouch in which the opening defines the distribution orifice 32 . in this case , the tray 31 will only act as a contact surface and a reception surface to recover the fluid product . optionally , the body 3 may be formed with a cover 36 that is connected in a single piece through a material bridge 37 to the rest of the body 3 . this material bridge 37 thus forms a pivoting hinge by which the cover 36 can be pivoted with respect to the skirt 33 and the tray 31 . the lower face of the cover 36 defines a suitably shaped closing needle 38 that fits into the distribution orifice 32 in a sealed manner to hermetically close it . this is the case when the cover 36 is folded over onto the plate 31 . with the dispenser according to the invention , it is possible to obtain a dose of fluid product with a volume that is directly proportional to the rotation of the actuation means .