Abstract: The invention relates to a plastic sealing screw cap with an improved tamper-proof strip, intended for containers provided with a ring of the "Pilferproof" type having a threading above a counter-ring whose lower part forms a raised edge, the cap having a head, a skirt provided with an inner threading, and a tamper-proof strip connected to the lower part of the skirt by a multiplicity of bridges constituting connections that can be broken. The tamper-proof strip has two parts, a first annular part (4A) connected to the lower part of the skirt (2) by the bridges that can be broken (5) and a second part consisting of a multiplicity of tabs (6) connected to the first part (4A) by thinner areas (7) forming a hinge, each tab having a heel (8) and a thinner extension (9). The tabs (6) form with the annular part (4A) an acute angle having its apex on the thinner areas (7) and are turned to the inside of the cap. Sealing means are explained.