A vial for fluid products, particularly pharmaceutical, cosmetic, medical products, or the like, comprising: - a containment body for a fluid product, provided with a product dispensing mouth; - a closing means which: in an initial configuration, is joined to said containment body along a predetermined breaking line to close the dispensing mouth and, in an opening configuration, obtained by tearing said predetermined breaking line, is separated from said containment body to open said dispensing mouth; - an opening key which: in the initial configuration, is slidingly fitted onto the closing means and is rotationally released from said closing means; in a working configuration, is prismatically rotationally engaged with said closing means to put pressure thereon and remove it from said containment body to obtain the opening configuration; wherein the closing means comprises an upper portion provided with prismatic protrusions interspersed with recesses, and the opening key comprises a prismatic coupling seat with a bottom provided with prismatic protrusions interspersed with recesses, and wherein in the working configuration the prismatic protrusions of the closing means are inserted into the recesses of the opening key, and wherein said prismatic protrusions (41,51) are flared and they widen at the base so that the respective recesses (42,52) narrow at the base. - a containment body for a fluid product, provided with a product dispensing mouth; - a closing means which: in an initial configuration, is joined to said containment body along a predetermined breaking line to close the dispensing mouth and, in an opening configuration, obtained by tearing said predetermined breaking line, is separated from said containment body to open said dispensing mouth; in an initial configuration, is joined to said containment body along a predetermined breaking line to close the dispensing mouth and, in an opening configuration, obtained by tearing said predetermined breaking line, is separated from said containment body to open said dispensing mouth; - an opening key which: in the initial configuration, is slidingly fitted onto the closing means and is rotationally released from said closing means; in a working configuration, is prismatically rotationally engaged with said closing means to put pressure thereon and remove it from said containment body to obtain the opening configuration; wherein the closing means comprises an upper portion provided with prismatic protrusions interspersed with recesses, and the opening key comprises a prismatic coupling seat with a bottom provided with prismatic protrusions interspersed with recesses, and wherein in the working configuration the prismatic protrusions of the closing means are inserted into the recesses of the opening key, and wherein said prismatic protrusions (41,51) are flared and they widen at the base so that the respective recesses (42,52) narrow at the base. in the initial configuration, is slidingly fitted onto the closing means and is rotationally released from said closing means; in a working configuration, is prismatically rotationally engaged with said closing means to put pressure thereon and remove it from said containment body to obtain the opening configuration; wherein the closing means comprises an upper portion provided with prismatic protrusions interspersed with recesses, and the opening key comprises a prismatic coupling seat with a bottom provided with prismatic protrusions interspersed with recesses, and wherein in the working configuration the prismatic protrusions of the closing means are inserted into the recesses of the opening key, and wherein said prismatic protrusions (41,51) are flared and they widen at the base so that the respective recesses (42,52) narrow at the base.