Abstract: A magnet holder accessory for releasable solely magnetic mounting to a metal oil filter cartridge has a magnet housing wherein the magnet housing consists essentially of an upper surface member an opposite lower surface member and side surface members extending around so as to enclose a magnet retaining cavity within the magnet housing, the side surface members contiguous to the perimeter of the lower surface member and the upper surface member, the magnet retaining cavity sized to snugly retain a magnet within the cavity a first distance from a lower surface of the lower surface member and a second distance from an upper surface of the upper surface member, wherein the first distance is a relatively small distance for minimizing attenuation of magnetic force of a magnet within the magnet retaining cavity, and the second distance is a distance significantly larger than the first distance so as to attenuate the magnetic force from the magnet retained within the magnet retaining cavity.