Nws yog ib hom hollow ntev ncig steel, feem ntau yog siv rau hauv roj av, tshuaj, tshuaj, khoom noj khoom haus, lub teeb kev lag luam, mechanical instrumentation thiab lwm yam kev thauj mus los kav thiab mechanical qauv qhov chaw.Tsis tas li ntawd, hauv kev khoov, lub zog torsional yog tib yam, lub teeb yuag, yog li nws kuj tau siv dav hauv kev tsim cov khoom siv tshuab thiab cov qauv tsim vaj tsev.