Abstract: A device is provided capable of regulating the length of the string of a necklace of the type provided with a chain or other filiform element for support of a pendant for ornamental use produced in the jewelry field and costume jewelry such for example a “collino” which is a thin chain to be used around the neck on which a little medal or a little cross can be hanged, a bracelet, an earring and similar products. The device has a particular conformation of the means capable of regulating in the desired manner the length of the chain or the other filiform structure.