A pull-off closure for containers having an opening whose end portion defines an annular collar projecting externally; the closure comprising: - a metal shell having an upper face from which extends a collar , which collar is turned over to abut on the annular collar of the container, during capping of the container, the upper face and the collar forming, at their connection, an annular edge ; - a first and a second line of weakness formed on the metal shell as internal incisions and forming an opening strip which extends in a tab extending beyond the collar ; - a gripping element associated with the tab , the first and second line of weakness extend only on the collar outside the annular edge and wherein the first and a second lines of weakness are symmetrical with respect to a second axis (Y) at the centre of the tab and passing through a centre of the upper face , wherein each line of weakness starts from a median end point located outside the above-mentioned tab and terminates beyond a first axis (X) perpendicular to the second axis (Y) and passing through the centre of the upper face , at a transversal end point , characterised in that the lines of weakness have a initial zone with reduced depth, a ratio between the distance (LA) between the two median end points , proximal to the tab , measured parallel to the first axis (X) passing through the centre and parallel to the upper face , and the diameter (D) of the upper face is between 0.5 and 0.7 and wherein a ratio between the distance (LB) between the two transversal end points distal from the tab , and the first axis (X), measured parallel to the second axis (Y) at right angles to the first axis (X) and passing through the centre and parallel to the upper face , and the diameter (D) of the upper face is between 0.1 and 0.2, wherein each line of weakness starts at an edge of the collar and ends at a predetermined distance (DT) from the edge of the collar , measured as a projection on the first axis (X) of the shell in the flat configuration, of between 0.5 and 4 mm and wherein the first and the second line of weakness are both curved. - a metal shell having an upper face from which extends a collar , which collar is turned over to abut on the annular collar of the container, during capping of the container, the upper face and the collar forming, at their connection, an annular edge ; - a first and a second line of weakness formed on the metal shell as internal incisions and forming an opening strip which extends in a tab extending beyond the collar ; - a gripping element associated with the tab , the first and second line of weakness extend only on the collar outside the annular edge and wherein the first and a second lines of weakness are symmetrical with respect to a second axis (Y) at the centre of the tab and passing through a centre of the upper face , characterised in that the lines of weakness have a initial zone with reduced depth, a ratio between the distance (LA) between the two median end points , proximal to the tab , measured parallel to the first axis (X) passing through the centre and parallel to the upper face , and the diameter (D) of the upper face is between 0.5 and 0.7 and wherein a ratio between the distance (LB) between the two transversal end points distal from the tab , and the first axis (X), measured parallel to the second axis (Y) at right angles to the first axis (X) and passing through the centre and parallel to the upper face , and the diameter (D) of the upper face is between 0.1 and 0.2, wherein each line of weakness starts at an edge of the collar and ends at a predetermined distance (DT) from the edge of the collar , measured as a projection on the first axis (X) of the shell in the flat configuration, of between 0.5 and 4 mm and wherein the first and the second line of weakness are both curved. <EOS>