A filter unit (3) for inserting into a blood vessel (1) is disclosed, the filter unit (3) comprising: —a stent-like body (2) having a superior end (4) and a inferior end (5), the stent-like body (2) being able to expand in order to engage a wall of the blood vessel (1), —two cone-shaped units (6, 7) each having a base opening (8, 9) and a tip (10, 11), one base opening (8) being operatively connected to the superior end (4) of the stent-like body (2), the other base opening (9) being operatively connected to the inferior end (5) of the stent-like body (2), wherein the tips (10, 11) of the cone-shaped units (6, 7) point towards each other.
