Safety fitting, namely backflow preventer or system separator, with a housing which has at least an inlet, an outlet and a drain, with a closure body which is positioned in the housing and via which, in a first position, the inlet and the outlet are connectable blocking the outlet and via which, in a second position, the inlet and the outlet are separable opening up the outlet, and with a sealing ring which interacts with the closure body and is accommodated in a recess of the housing, wherein the sealing ring has a radially inner contour facing the closure body and a radially outer contour facing the housing, wherein the radially inner contour of the sealing ring comprises a first inner sealing contour, which is designed as a sealing lip on an input-side portion of the sealing ring and, at least in the second position of the closure body, bears against an outer contour of same and, at least in the second position of the closure body, provides a sealing function between the sealing ring and the closure body in the event of a positive pressure difference between an input-side pressure applied to the sealing ring and an output-side pressure applied to the sealing ring, and comprises a further, second inner sealing contour which is designed as a sealing lip on an output-side portion of the sealing ring and, at least in the second position of the closure body, likewise bears against the outer contour of same and, in the event of a negative pressure difference between an input-side pressure and an output-side pressure, provides a sealing function between the sealing ring and the closure body, wherein the sealing ring is contoured asymmetrically and, opposite the two radially inner sealing contours (21, 22), comprises a respective radially outer projection (25, 26) on the radially outer contour, wherein the radially outer projections (25, 26) of the sealing ring each bear against the recess for receiving the sealing ring, characterized in that the sealing ring is asymmetrically contoured in such a manner that either the outer projection, which is formed on the input-side portion of the sealing ring, and the inner sealing contour, which is opposite said outer projection on the input-side portion of the sealing ring, are contoured dissimilarly, whereas the outer projection, which is formed on the output-side portion of the sealing ring, and the inner sealing contour, which is opposite said outer projection on the output-side portion of the sealing ring, are contoured similarly, namely as a sealing lip; or the outer projection, which is formed on the input-side portion of the sealing ring, and the inner sealing contour, which is opposite said outer projection on the input-side portion of the sealing ring, are contoured similarly, namely as a sealing lip, whereas the outer projection, which is formed on the output-side portion of the sealing ring, and the inner sealing contour, which is opposite said outer projection on the output-side portion of the sealing ring, are contoured dissimilarly, wherein the respective outer projection which is contoured dissimilarly to the inner sealing contour is contoured in a trapezoidal or spherical manner in cross section.