A piston ring and a piston combination comprising A piston ring having a running surface, an inner surface, a lower ring flank, and an upper ring flank; wherein a recess, extending across the perimeter in the shape of an internal angle, is located at the transition between the inner surface and the upper ring flank; wherein the recess defines a conical first surface and a conical second surface at the piston ring, wherein the first surface lies further outward, when viewed in the radial direction, and further above, when viewed in the axial direction, than the second surface; wherein, in an axial cross section, a first angle (α) between the axial direction and the first surface lies in the range between 10 ° and 50 °, and a second angle (β) between the radial direction and the second surface lies in the range between 5 ° and 30 °, a piston having a piston ring groove having a groove bottom and a lower groove flank, wherein a projection is arranged at an upper end of the groove bottom of the piston ring groove; wherein the projection has a conical first projection surface and a conical second projection surface, wherein the first projection surface lies further outward, when viewed in the radial direction, and further above, when viewed in the axial direction, than the second projection surface, wherein, in an axial cross section, a third angle (α k) between the axial direction and the first projection surface lies in the range between 10 ° and 50 °, and a fourth angle (β k) between the radial direction and the second projection surface lies in the range between 5 ° and 30 °; wherein the recess and the projection are designed such that, when the piston ring is mounted in the piston ring groove, the projection projects into the recess, the second surface extends parallel to the second projection surface, and the first surface extends parallel to the first projection surface or the first angle (α) between the axial direction and the first surface is greater than the third angle (α k) between the axial direction and the first projection surface wherein, when the piston ring is mounted in the piston ring groove and the second surface contacts the second projection surface, an axial distance (h m) exists between the first surface, and the first projection surface and wherein the piston ring groove additionally comprises an upper groove flank, characterized in that when the piston ring is mounted in the piston ring groove and the second surface contacts the second projection surface, an axial distance (h ax) exists between the upper ring flank and the upper groove flank. A piston ring having a running surface, an inner surface, a lower ring flank, and an upper ring flank; wherein a recess, extending across the perimeter in the shape of an internal angle, is located at the transition between the inner surface and the upper ring flank; wherein the recess defines a conical first surface and a conical second surface at the piston ring, wherein the first surface lies further outward, when viewed in the radial direction, and further above, when viewed in the axial direction, than the second surface; wherein, in an axial cross section, a first angle (α) between the axial direction and the first surface lies in the range between 10 ° and 50 °, and a second angle (β) between the radial direction and the second surface lies in the range between 5 ° and 30 °, a piston having a piston ring groove having a groove bottom and a lower groove flank, wherein a projection is arranged at an upper end of the groove bottom of the piston ring groove; wherein the projection has a conical first projection surface and a conical second projection surface, wherein the first projection surface lies further outward, when viewed in the radial direction, and further above, when viewed in the axial direction, than the second projection surface, wherein, in an axial cross section, a third angle (α k) between the axial direction and the first projection surface lies in the range between 10 ° and 50 °, and a fourth angle (β k) between the radial direction and the second projection surface lies in the range between 5 ° and 30 °; wherein the recess and the projection are designed such that, when the piston ring is mounted in the piston ring groove, the projection projects into the recess, the second surface extends parallel to the second projection surface, and the first surface extends parallel to the first projection surface or the first angle (α) between the axial direction and the first surface is greater than the third angle (α k) between the axial direction and the first projection surface wherein, when the piston ring is mounted in the piston ring groove and the second surface contacts the second projection surface, an axial distance (h m) exists between the first surface, and the first projection surface and wherein the piston ring groove additionally comprises an upper groove flank, characterized in that when the piston ring is mounted in the piston ring groove and the second surface contacts the second projection surface, an axial distance (h ax) exists between the upper ring flank and the upper groove flank.