Within a specific class of pipe, the outside diameter of heavy-weight pipe is:

The choice stating that the outside diameter of heavy-weight pipe is the same as the outside diameter of standard weight pipe is accurate because, in non-ferrous piping systems such as those used in refrigeration, the outside diameter of pipes tends to be standardized across different weight classes. This means that when comparing pipes of the same nominal size (which refers to the inside diameter), their outside diameters remain consistent regardless of whether they are classified as standard weight or heavy-weight. The difference between these types of pipes lies in their wall thickness, which ultimately affects their pressure rating and overall strength but not their external dimensions.

Thus, since both pipe classes are designed to fit the same fittings and connections, maintaining a consistent outside diameter is crucial for compatibility in installation. This design standardization facilitates easier assembly and maintenance across various piping systems.