Kev sib dhos yooj yim steel placon menyuam sib koom nrog vuam tuav ntug rau hom 40 cov menyuam taug qab.
Peb yog cov chaw tsim khoom ntawm steel roller taug kev sib koom ua ke.Peb cov khoom muag ncaj qha los ntawm cov chaw tsim khoom.Nrog tus nqi qis thiab kev xa khoom loj, peb yog qhov kev xaiv zoo tshaj plaws rau cov neeg muag khoom.