Abstract: A seal includes an annular main member. A seal lip is projected inwards from the annular main member, wherein the seal lip has a tip and an outer inclined surface a plurality of helixes are projected from the outer inclined surface of the seal lip, each of which has a first extending section along a first direction and a second extending section along a second direction connected to the first extending section. The first extending section has a first free end and the second extending section has a second free end, and a junction of the first extending section and the second extending section is a turning point. A first angle is between each of the first directions and a corresponding tangent line of the tip, and a second angle is between each of the first direction and the second direction.