This is because the skin is not capable of stretching quickly enough if the bullet's velocity is too high. If the wound is made over bone, such as a head wound in the scalp, the abrasion collar may not be round at all; it instead becomes stellate or "star-shaped" with ragged and torn edges caused by the skin over-stretching and tearing. In the case of skull entrance wounds, the skin that includes the abrasion collar may be torn away because the underlying tissue is unable to flex away from the force of the bullet's entry.[1]