An apparatus for treating vascular aneurysms includes an occlusive support device comprised of one or more support members. The occlusive device has, an end cap member and an anchoring member. The end cap member is comprised of at least one of one or more of the support members. The end cap member has openings and the end cap member comprises a reactive material that is configured to hydrate upon delivery of the device and to reduce the size of said openings. The device is configured so that the occlusive members can be positioned in the blood vessel proximate the neck of a vascular aneurysm, the reactive material hydrates and increases the resistance to blood flow into the aneurysm, and the anchoring member anchors the device in the blood vessel without occluding flow through the blood vessel.