Abstract: A valve apparatus for controlling fluid flow therethrough. A valve support body attached to an elongated stem is housed in an internal opening of a valve body which is externally mateable with a valve seat. Mateable surfaces on the valve body and valve seat are spherical so as to ensure complete engagement therebetween for misalignments between the stem-supported valve body and the valve seat. An antivibration or stabilizing ring situated between the support body and the valve body within the internal opening permits rotation of the valve body about the support body during valve closure to compensate for large stem-valve seat misalignments while restricting relative oscillatory, vibrating motion between the support body and valve body when the valve is in the open, unengaged configuration. Maximum vibration resistance and free rotatability of the valve body is obtained by disposing the stabilizing ring to occupy a position in the plane formed by the contact line between the valve body and seat.