A gasket (5) and an assembly (1) for a plate heat exchanger are provided. The gasket (5) comprises an elongate body (45) and a first number ≥1 of elongate projections (47, 49, 51) projecting from an upper side (53) of the body (45) and extending along a longitudinal extension (L) of the gasket (5). Each of the projections (47, 49, 51) is defined by a top (57) and two opposing flanks (59, 61) extending from the top (57) to the body (45) of the gasket (5). The gasket is characterized in that, with reference to a cross section through, and perpendicular to the longitudinal extension (L) of, the gasket (5), for each of a second number ≥1 of unsymmetrical projections (47, 51) of said projections (47, 49, 51), a first area (a1) defined by an outer flank (59, 61) of said flanks (59, 61), the upper side (53) of the body (45) and a normal (n) of the upper side (53) of the body (45) extending through the top (57) of the unsymmetrical projection (47, 51), is smaller than a second area (a2) defined by an inner flank (59, 61) of said flanks (59, 61), the upper side (53) of the body (45) and said normal (n) of the upper side (53) of the body (45) extending through the top (57) of the unsymmetrical projection (47, 51). This normal is displaced from a center normal (nc) of the upper side (53) of the body (45) aligned with a longitudinal center axis (C) of the gasket body (45). Further, the body (45) forms a ledge (67) on a respective outside of the outer flanks (59, 61).