A seal assembly (1) adapted to be interposed between first and second relatively rotatable members (2, 3) and comprising first and second sealing screens (6, 7) closing an annular cavity (8) defined by the first and second members (2, 3); the second screen (7) facing towards the outside of the cavity (8) and having an annular lip (26) with a radial projection (28) adapted for slidable cooperation with a surface (15) of the first screen (6), and an annular end portion (29) able to cooperate axially with a shoulder (33) for one of the members (2, 3), this shoulder being outside the cavity (8); between the radial projection (28) and the end portion (29) a radial undercut (35) is formed on the annular ring, the said undercut (35) forming a virtual hinge permitting deformations of the end portion (29) without causing corresponding deformations of the annular lip (26) at the radial projection (28).