A cap for glass bottles, comprising a first body and a second body integrally attached to the first body, wherein: a) the first body comprises: a. a skirting with at least three cuts made from the outside of the skirting to the inside of the body; characterised in that the first body further comprises: b. a core with at least three reinforcement ribs arranged to not deform during opening; c. a first externally concave region or area provided inside the first body and coincident with the position of the core; b) the cap being further characterised in that the second body comprises: a. a flange incorporating a plurality of cuts around the periphery configured for: i. fitting onto the outer surface of a rim of the glass bottle; ii. fitting onto the skirting of the body creating a second externally concave region in the central part therein; b. a threaded region in the lower part of the second body in turn comprising: i. a plurality of crests improving grip on a neck of the glass bottle and providing the sealing required for properly preserving a liquid contained in the bottle; and c. a plurality of reinforcement spokes contiguous to the threaded region; wherein the first concave region or area that coincides with the second concave region or area are opposite one another, such that they define a chamber or space there between configured for the tilting of the edge of the cap during the deformation thereof in the process of opening it. a) the first body comprises: a. a skirting with at least three cuts made from the outside of the skirting to the inside of the body; characterised in that the first body further comprises: b. a core with at least three reinforcement ribs arranged to not deform during opening; c. a first externally concave region or area provided inside the first body and coincident with the position of the core; a. a skirting with at least three cuts made from the outside of the skirting to the inside of the body; characterised in that the first body further comprises: b. a core with at least three reinforcement ribs arranged to not deform during opening; c. a first externally concave region or area provided inside the first body and coincident with the position of the core; b) the cap being further characterised in that the second body comprises: a. a flange incorporating a plurality of cuts around the periphery configured for: i. fitting onto the outer surface of a rim of the glass bottle; ii. fitting onto the skirting of the body creating a second externally concave region in the central part therein; b. a threaded region in the lower part of the second body in turn comprising: i. a plurality of crests improving grip on a neck of the glass bottle and providing the sealing required for properly preserving a liquid contained in the bottle; and c. a plurality of reinforcement spokes contiguous to the threaded region; a. a flange incorporating a plurality of cuts around the periphery configured for: i. fitting onto the outer surface of a rim of the glass bottle; ii. fitting onto the skirting of the body creating a second externally concave region in the central part therein; i. fitting onto the outer surface of a rim of the glass bottle; ii. fitting onto the skirting of the body creating a second externally concave region in the central part therein; b. a threaded region in the lower part of the second body in turn comprising: i. a plurality of crests improving grip on a neck of the glass bottle and providing the sealing required for properly preserving a liquid contained in the bottle; and i. a plurality of crests improving grip on a neck of the glass bottle and providing the sealing required for properly preserving a liquid contained in the bottle; and c. a plurality of reinforcement spokes contiguous to the threaded region;