Abstract: A wellhead assembly having an inner tubular insertable into an outer tubular. A packoff is provided on an outer surface of the inner tubular for sealing between the inner and outer tubulars. The packoff includes an energizing ring, a U-shaped seal member, and a nut for retaining the seal member against the energizing ring. The seal member includes legs that are spaced apart by interaction with the energizing ring. The outer tubular has a bore wall that is profiled so that when the inner tubular is inserted into the outer tubular, an outer leg of the seal member is spaced radially outward from the bore wall until the inner tubular is landed in the outer tubular. When the inner tubular member is landed, a portion of the bore wall adjacent the outer leg tapers radially inward into sealing contact with the outer leg of the seal member.