Lip type seal

Lip shaft disposed in the housing (12) and reciprocating (1), with the mating member is prevented (12 or 13) in close contact with the resin sealing an annular gap between the lip (13) of (3 , 4,6) of the front end (31,41,61) of shape changes with time, further, the shape of the front end of the lip (3,4,6) of (31,41,61) and having a cusp-shaped to ensure a functional characteristics of low leakage and to ensure the oil film thickness to function as the shape feature R balance. As a solving means, the respective lips (3,4,6) of the front end (31,41,61), forming a flat surface (21) has an edge portion (22) of the axial width (W) of. Further, the axial width of the flat surface (21) in (W) of each of the lips (3,4,6) the total axial width (A) 5 to 30%.