In general, there are two kinds of 55 gallon plastic drum open (removable head) and closed (non-removable head) top. Closed top type is used as packaging for liquid chemical. It has 2 drum plugs, 2″ NPT and 3/4″ NPT. But, some of them may have only one plug.
55 gallon plastic drum is common packaging that is used for storing water, solid material or liquid chemicals. In chemical industry, 55 gallon plastic drum is especially used as packaging for various kinds of chemicals due to its perfect chemical resistant.