This steel plug has 1/8 NPT pipe threads and a hex recess. This plug is used to plug just one or two holes in the FF1600 engine block. The factory hole is located between the motor mount bosses on the carburetor side of the block. You may also find that the original dipstick hole (near the bell housing flange, on the carburetor side) has been tapped to accept this plug. Sold individually.