The disclosure provides a filter apparatus and method of filtering in a body vessel. The filter apparatus comprises a filter unit and an expandable introducer designed to deliver the filter unit to the target filtering site. The filter unit attaches to the expandable introducer via a plurality of anchors on the filter unit. The expandable introducer delivers and presses the anchors to the vessel wall during implantation. After implantation, the filter unit exerts minimal or about zero radial force against the vessel wall.
