3.Elliptic tube: elliptic tube he huahana hou i hoʻokomoʻia i nā makahiki i hala iho nei.Hoʻohālikelike ʻia me ka puʻupuʻu pōʻai, ʻoi aku ka maikaʻi o ka puʻupuʻu elliptic.Eia naʻe, no ka mea, ua hana ʻia ka paipu elliptic i kēia manawa me ka lipine galvanized, ʻoi aku ka haʻahaʻa o kāna hana anti-corrosion ma mua o ka paipu circular.
4.Profile Steel: hoʻohana ʻia ia ma luna o ka hale ʻōmaʻomaʻo naʻauao e hana i kahi kiʻi kila.Loaʻa iā ia ka maikaʻi o ka haʻahaʻa haʻahaʻa a me ka maikaʻi ʻole i ka hoʻohālikelike ʻia me ka paipu square.Hoʻohana nui ʻia ia i nā wahi me ka haʻahaʻa haʻahaʻa a me nā koi pale corrosion.