A rotary positive displacement pump for pumping a fluid product, the pump having a front side and a rear side and comprising: a main body providing rotational support to a pair of parallel, axially extending, shafts (4, 5) with gears (6, 7) in constant mesh condition, such that the pair of shafts (4, 5) are arranged to rotate in opposite directions, a rotor case body connected to a front side of the main body and having: - a stationary interior pumping cavity defined by an axial rear wall, a circumferential side wall, and a removable front cover, - a fluid product inlet opening, - a fluid product outlet opening, and - a pair of cylindrical rotor case hubs (36, 37) extending from the rear wall, wherein each cylindrical rotor case hub (36, 37) receives internally one of the pair of shafts (4, 5), a pair of rotors (23, 24), each having at least one rotor wing and a rotor drive element that is mounted torque proof on a rotor seat at an end region of one of the pair of shafts (4, 5), wherein each of the pair of rotor seats has an axial abutment surface facing in an axial direction towards a front side of the pump and a mounting surface facing radially outwards, wherein the pump further comprises a pair of fasteners, each being engaged with a mating section at the end region of one of the pair of shafts (4, 5), and each exerting an axial clamping force on one of the rotor drive elements against the axial abutment surface of one of the rotor seats, and characterized in that the axial abutment surface of each rotor seat is located axially outside, towards a front side, of the associated hub (36, 37). a main body providing rotational support to a pair of parallel, axially extending, shafts (4, 5) with gears (6, 7) in constant mesh condition, such that the pair of shafts (4, 5) are arranged to rotate in opposite directions, a rotor case body connected to a front side of the main body and having: - a stationary interior pumping cavity defined by an axial rear wall, a circumferential side wall, and a removable front cover, - a fluid product inlet opening, - a fluid product outlet opening, and - a pair of cylindrical rotor case hubs (36, 37) extending from the rear wall, wherein each cylindrical rotor case hub (36, 37) receives internally one of the pair of shafts (4, 5), - a stationary interior pumping cavity defined by an axial rear wall, a circumferential side wall, and a removable front cover, - a fluid product inlet opening, - a fluid product outlet opening, and - a pair of cylindrical rotor case hubs (36, 37) extending from the rear wall, wherein each cylindrical rotor case hub (36, 37) receives internally one of the pair of shafts (4, 5), a pair of rotors (23, 24), each having at least one rotor wing and a rotor drive element that is mounted torque proof on a rotor seat at an end region of one of the pair of shafts (4, 5), wherein each of the pair of rotor seats has an axial abutment surface facing in an axial direction towards a front side of the pump and a mounting surface facing radially outwards, wherein the pump further comprises a pair of fasteners, each being engaged with a mating section at the end region of one of the pair of shafts (4, 5), and each exerting an axial clamping force on one of the rotor drive elements against the axial abutment surface of one of the rotor seats, and characterized in that the axial abutment surface of each rotor seat is located axially outside, towards a front side, of the associated hub (36, 37).