Abstract: A plurality of permanent magnets contained within a flexible non-magnetic strap assembly which is wrapped about the exterior casing of an oil filter or a conduit for other fluids or particulate substances. The magnetic force fields created by the magnets penetrate the interior of the casing or conduit to attract and capture magnetizable particles entrained within the fluid or other substance and retain them against the interior peripheral wall of the casing or conduit. The flexible magnetic strap assembly may be spirally wound about the container for an oil filter, or the conduit for other fluids or particulate substances any number of times to thus maximize the magnetic effect and to fit different size containers or conduits. The flexible magnetic strap assembly may be elastic, with adjustable or non-adjustable joining devices at the ends, or the ends may be permanently joined, to enable fitting the elongated flexible and elastic magnetic strap to different size containers and conduits.