Fastening device for sealing a fluid product reservoir

A fastener device for closing a fluid reservoir that is formed with a neck that is provided with outer peripheral reinforcement that co-operates with the remainder of the neck to define a bottom shoulder, the fastener device comprising a fastener ring configured to hold a closure member on the neck, the fastener ring including a peripheral skirt configured to engage axially around the neck to below the bottom shoulder, the skirt provided with fastener elements that each form a contact zone configured to bear against the neck with at least one coming into bearing engagement with the neck below the bottom shoulder, so as to fasten the ring on the neck;

• wherein the contact zones are situated at different axial heights on the inner periphery of the skirt without axially overlapping, such that some contact zones come into operating engagement below the bottom shoulder, while other contact zones do not come into operating engagement below the bottom shoulder of the neck;
• and
• wherein each fastener element extends downwards from a proximal base of the fastener element attached to the skirt to a free distal edge of the fastener element.