Spongy ferrous products (DRI/HBI) are produced by solid-state reduction of iron ore without melting, resulting in a porous, carbon-lean material distinct from blast-furnace pig iron. The key classification markers are the production route, carbon content, and physical form — pig iron is cast in molten form, while DRI/HBI retains a sponge-like or briquetted structure. Mill test reports and production process documentation are typically required to support the correct SITC/HTS classification.

DRI and HBI provide a low-residual, consistent-chemistry iron unit that dilutes copper, tin, and other tramp elements accumulated in scrap-heavy heats. This is especially important for producing flat-rolled and other quality steel grades where residual limits are tight. Supply availability and ocean freight logistics — particularly for bulk shipments — are the primary sourcing constraints.