US Patent 7582020 Boot for universal joint

In a universal joint boot including a bellows part, a ring-shaped mounting part that is formed at one end of the bellows part and into which a cup for receiving one member of two members moving relatively to each other is inserted; and a seal that is formed toward the peripheral direction of the inner peripheral surface of the mounting part to which the cup is mounted, the inner peripheral surface has protrusions protruding toward the axial center of the ring-shaped mounting part and the height of the seal lip becomes lower from the bottom of the protrusion to a peak and width of the seal lip becomes wider from the bottom of the protrusion to the peak, whereby sealing performance can be improved.