The “L Series” fixed flow-rate volumetric dosing valve differs from the “Z Series” volumetric dosing valve in its compactness, reduced sized, direct locking of the pipe Ø4 for the service. Like the “Z Series,” it is characterized by the fact that at the lubricant inlet there is a special valve, patented for Italy, USA, Germany, Mexico, Canada and Saudi Arabia, and in the general construction context it is distinguished by having a double seal in the two phases of Work and Pause.