Abstract: A fluid dispenser comprising: a fluid reservoir (1) having a neck (11) defining an opening (10) and an axis X, the neck (11) projecting axially from a shoulder (13); and a dispenser unit (D) comprising a dispenser member (4), such as a pump or a valve, and a fastener system (2, 31) for fastening the dispenser member (4) on the neck (11) of the reservoir (1), the fastener system comprising a fastener ring (2) that is engaged with the neck (11) and a blocking hoop (31) that is engaged axially around the ring (2) for blocking the ring on the neck in the final assembled position; disassembly means (14, 34) for axially moving the hoop (31) relative to the ring (2), from the final assembled position to a disassembled position in which the hoop does not block the ring on the neck, such that the unit (D) can be removed from the neck (11), the disassembly means comprising two elements (14, 34) capable of turning mutually relative to each other about the axis X, the dispenser being characterized in that one element

Abstract: A welding ring is made as a flat ring body, of internal diameter equal to e internal diameter of the parts to be assembled and of outer diameter in excess of the external diameter of the parts to be assembled by the mount of a peripheral edge on each face of which are regularly distributed alternately six locating reliefs which are placed in abutment against the outer diameters of the parts to be assembled. A method of welding with such a ring is also described.