The goal of the present invention is to develop a vein filter concept that has a small diameter in the collapsed state and is easy to position without the risk of the legs becoming entangled when deploying the filter. This goal is attained by a vein filter 1 that can switch from a collapsed state to a deployed state and that comprises at least four legs 10a, 10b extending from the filter head 2 to a free end. The vein filter of the invention is characterised in that said four legs are organized in facing pairs 10a, 10b said facing pairs of legs having different lengths.
