Steel drum plastic bung is G2 and G3/4'' plug type with ISO-228 thread, can well suit into drum flange on 55 gallon steel drums. It is a substitute for zinc plated drum plug in some cases. Whatever the material is, the bungs are aiming at reducing the risk of spillage and keeping the contents safe.
The included 2'' and 3/4'' bung fittings make filling and dispensing easy and convenient, the plug wrench is designed to help to screw in and out of the bung fittings.