Designed for use in corrosive environments to seal extra pushbutton holes, conduit openings and knockout openings against dust, dirt, oil and water. These hole seals are suitable for sealing enclosure openings in industries such as petroleum and chemical processing, wastewater processing, pulp and paper, outdoor monitoring and any other industry exposed to harsh environments. Innovative 3-in-1 self-centering design • Thread self-centers on one hole size • Nut orientation "A" self-centers on a second hole size (see Nut Orientation drawing) • Nut orientation "B" self-centers on a third hole size