- A bistable hinge element for an eyeglasses frame, comprising: • an arm cage having a bottom extended laterally by two longitudinal side walls which define a housing (251, 252) that opens onto the proximal transverse face through an opening that is U-shaped in cross-section, each one of said side walls having an upper lip (250, 260) extending from said proximal transverse face to an intermediate portion of said housing, said lips (240, 250) delimiting a gap whereof the width corresponds to the width of said U-shaped opening, • a front cage having a bottom which is extended laterally by two longitudinal side walls which define a housing (151, 152) that opens onto the proximal transverse face through an opening that is U-shaped in cross-section, each one of said side walls having an upper lip (150, 160) which extends from said proximal transverse face to an intermediate portion of said housing, said lips (150, 160) delimiting a gap whereof the width corresponds to the width of said U-shaped opening, • said proximal faces (121, 221) having complementary guiding slider segments (121, 125, 211, 225), which are perpendicular to the plane of said gap, said guiding slider segments (121, 125) of the front cage being extended on the surface of said lips (150, 160) by guiding slider segments (122, 126) that extend from one side to the other of said gap, over a length that corresponds to the height of the proximal face of the arm cage, • a solid body that is elastically deformable along the longitudinal axis, and which has a central portion, with a cross-section corresponding to the transverse cross-section of said U-shaped openings, which is extended at each end by a bulge (330, 350) of a cross-section that is complementary to the transverse cross-section of said housings of the arm and front cages. • an arm cage having a bottom extended laterally by two longitudinal side walls which define a housing (251, 252) that opens onto the proximal transverse face through an opening that is U-shaped in cross-section, each one of said side walls having an upper lip (250, 260) extending from said proximal transverse face to an intermediate portion of said housing, said lips (240, 250) delimiting a gap whereof the width corresponds to the width of said U-shaped opening, • a front cage having a bottom which is extended laterally by two longitudinal side walls which define a housing (151, 152) that opens onto the proximal transverse face through an opening that is U-shaped in cross-section, each one of said side walls having an upper lip (150, 160) which extends from said proximal transverse face to an intermediate portion of said housing, said lips (150, 160) delimiting a gap whereof the width corresponds to the width of said U-shaped opening, • said proximal faces (121, 221) having complementary guiding slider segments (121, 125, 211, 225), which are perpendicular to the plane of said gap, said guiding slider segments (121, 125) of the front cage being extended on the surface of said lips (150, 160) by guiding slider segments (122, 126) that extend from one side to the other of said gap, over a length that corresponds to the height of the proximal face of the arm cage, • a solid body that is elastically deformable along the longitudinal axis, and which has a central portion, with a cross-section corresponding to the transverse cross-section of said U-shaped openings, which is extended at each end by a bulge (330, 350) of a cross-section that is complementary to the transverse cross-section of said housings of the arm and front cages.