Heavy duty 4.5 inch replacement iron fire hydrant cap with NH / NST threads including chain. Pentagonal in shape.
The most common size and threads for US fire hydrants is 4 1/2" NH / NST. Outside diameter of a 4.5" male NH / NST adapter - 5.760 inches (4 Threads per inch). Inside diameter of the waterway is about 4.5 inches.
