Implantable occlusion devices that include one or more flanges extending from a tubular body are disclosed. The flange or flanges may assist in retention of the device within a vessel, cavity, appendage, etc. At least one flange on the occlusion device may include a concave surface proximate one end of a body. Because of the shape of the flange, e.g., its concavity, the occlusion device may resist dislocation due to e.g., the forces generated within the left atrial appendage during atrial fibrillation.
