Abstract: A filter for arresting the flow of a liquid entrained, deformable solid or semi-solid body through a tubular vessel or conduit, the filter including a plurality of convergent legs in generally conical array and joined at their convergent ends to an apical hub, each leg having a reversely bent hook at its end which is distal with respect to the hub. Each leg also includes a plurality of bends intermediate its length, which bends decrease the solids by-pass capability of the filter without concurrent fluid occlusion.An intrument for inserting the filter in a tubular environment is provided and includes a carrier for supporting the filter in a collapsed, compact status, an ejector mounted in the carrier for ejecting or releasing the filter from the carrier and an elongated flexible tube connected to the carrier for moving the carrier and filter to the locus of use of the filter, and for supplying an ejector actuating fluid to the ejector.