A vascular occluder includes a tubular support element and a sleeve of occluding material disposed within the support element. The sleeve is twisted in the support creating a constriction which closes the lumen of the sleeve. The lumen of the sleeve can nevertheless be opened by a guide wire or cannula for over the wire delivery. Once the guide wire or cannula are withdrawn from the sleeve, the sleeve will close again by the action of blood pressure thereon. Blood pressure will act to maintain closing pressure on the sleeve, thereby avoiding or reducing the risk of recanalization.