The invention refers to an apparatus which allows the application of a round gasket or liner inside closures. The apparatus consists of a plastic material batching carousel carrying, on a horizontal plate a plurality of shuttles or molds peripherically distributed and whose top surface is provided with a recess or hollow. On the carousel are elements which take and leave batches of plastic material supplied by an extruder inside the recesses. A first star wheel at the bottom of the carousel is provided to transfer the shuttles having the batches therein towards a forming carousel where the batches of plastic material are pressed to form round gaskets. A second star is provided to transfer the shuttles with the molded gaskets toward a further carousel where gaskets are inserted into cups or closures. The latter is provided with elements which conveys the cups along a way over the shuttles, while taking elements, placed on top of the conveyance elements, are provided to extract the round gaskets from the shuttles and to introduce them into the cups which, one at a time, come to be positioned under them. At the bottom of the inserting carousel a star wheel for moving away complete closures and a star wheel for transferring the evacuated shuttles towards the batching carousel are provided. It is also anticipated to use completely flat shuttles, that is to say without any recess. In this case, modified devices will be used in the forming carousel.