Railway or tramway sleepers (cross-ties) of wood

440611 Wood; railway or tramway sleepers (cross-ties), not impregnated, coniferous 440612 Wood; railway or tramway sleepers (cross-ties), not impregnated, non-coniferous 440691 Wood; railway or tramway sleepers (cross-ties), impregnated, coniferous 440692 Wood; railway or tramway sleepers (cross-ties), impregnated, non-coniferous