A filling unit for filling containing elements of single-use capsules with a dose of product for extraction or infusion beverages, comprising: - a line for transporting the containing elements extending along a first movement path and provided with a plurality of supporting seats for the containing elements arranged in succession along the first movement path; - a station for filling the above-mentioned containing elements with a dose of product; wherein the filling station comprises: - at least one first containing seat designed to receive a dose of product and movable along a second movement path; - a substation for forming the dose within the at least one first containing seat arranged at a region for forming the dose and provided with a device for releasing within the at least one first containing seat a predetermined quantity of product which defines the dose, the release device comprising a hopper and at least one first rotating element configured for rotating about a respective axis of rotation stationary with respect to the hopper, to create a feeding flow of product that intercepts the at least one first containing seat and to release the product within the at least one first containing seat; - at least one second containing seat designed to receive the dose of product from the at least one first containing seat and movable along a third movement path to convey the dose along said third movement path; characterised in that the filling station further comprises: - a substation for transferring the dose of product from the at least one first containing seat to the at least one second containing seat; - devices for moving the at least one first containing seat between the forming substation and the transfer substation and vice versa; - a substation for releasing the dose of product from the at least one second containing seat to a containing element transported by the transport line; - further moving devices for moving the at least one second containing seat between the transfer substation and the release substation, and vice versa. - a line for transporting the containing elements extending along a first movement path and provided with a plurality of supporting seats for the containing elements arranged in succession along the first movement path; - a station for filling the above-mentioned containing elements with a dose of product; wherein the filling station comprises: - at least one first containing seat designed to receive a dose of product and movable along a second movement path; - a substation for forming the dose within the at least one first containing seat arranged at a region for forming the dose and provided with a device for releasing within the at least one first containing seat a predetermined quantity of product which defines the dose, the release device comprising a hopper and at least one first rotating element configured for rotating about a respective axis of rotation stationary with respect to the hopper, to create a feeding flow of product that intercepts the at least one first containing seat and to release the product within the at least one first containing seat; - at least one second containing seat designed to receive the dose of product from the at least one first containing seat and movable along a third movement path to convey the dose along said third movement path; characterised in that the filling station further comprises: - a substation for transferring the dose of product from the at least one first containing seat to the at least one second containing seat; - devices for moving the at least one first containing seat between the forming substation and the transfer substation and vice versa; - a substation for releasing the dose of product from the at least one second containing seat to a containing element transported by the transport line; - further moving devices for moving the at least one second containing seat between the transfer substation and the release substation, and vice versa. - at least one first containing seat designed to receive a dose of product and movable along a second movement path; - a substation for forming the dose within the at least one first containing seat arranged at a region for forming the dose and provided with a device for releasing within the at least one first containing seat a predetermined quantity of product which defines the dose, the release device comprising a hopper and at least one first rotating element configured for rotating about a respective axis of rotation stationary with respect to the hopper, to create a feeding flow of product that intercepts the at least one first containing seat and to release the product within the at least one first containing seat; - at least one second containing seat designed to receive the dose of product from the at least one first containing seat and movable along a third movement path to convey the dose along said third movement path; - a substation for transferring the dose of product from the at least one first containing seat to the at least one second containing seat; - devices for moving the at least one first containing seat between the forming substation and the transfer substation and vice versa; - a substation for releasing the dose of product from the at least one second containing seat to a containing element transported by the transport line; - further moving devices for moving the at least one second containing seat between the transfer substation and the release substation, and vice versa.