A blood clot filter is collapsible toward a longitudinal axis into a collapsed configuration for insertion into a blood vessel, and is radially expandable outwardly from the longitudinal axis to an expanded configuration for contact with the inner wall of the blood vessel at two longitudinal spaced locations. A first plurality of spaced, elongate arms, in the expanded configuration, curve outwardly away from the longitudinal axis toward the leading end of the filter to form a first filter basket and to center a hub at the trailing end of the filter within the vessel. A second plurality of spaced elongate legs angle outwardly away from the longitudinal axis toward the leading edge of the filter in the expanded configuration to form a second filter basket opening toward the leading end. The ends of these legs include hooks to bend and straighten in response to withdrawal force.