BIKEMASTER MAGNETIC OIL DRAIN PLUG STEEL 12MM/1.5 Powerful magnets embedded in the plugs catch any ferrous metallic particles that might be scraped from cylinder walls or gears, etc. Simply clean metallic particles off next time you drain the oil Select by size Note: Check to ensure that there is sufficient clearance for magnetic drain plugs prior to use. Install the plug and slowly turn the engine over by hand, making sure that there is no contact with any internal engine components.