Magnetic sump plug, catches all the iron filings as your engine slowly wears. Can be used in gearbox and axle too.
Don't forget the fibre washer which is sometimes required.
This part is listed on the following pages of the website, where further information and background reading may be found.
Engine, Transmission, wheels/Tyres and Heating/Cooling »
ENGINE BLOCK PARTS
Engine, Transmission, wheels/Tyres and Heating/Cooling »
GEARBOX PARTS