Ntawm txhua tus hlau, hlau tau siv dav thiab muaj ntau hom.
Raws li cov pwm txawv, kev ua cov khoom sib txawv, qhov chaw ua haujlwm muaj peev xwm muab faib ua peb yam: 1. Ua haujlwm txias tuag steel, 2. Kub ua haujlwm tuag steel, 3. Yas tuag hlau. Aluminium ntawv ci tais pwm ua cov khoom yog txhuas ntawv ci ntawv, yog li thawj tus yuav tsum siv: txias ua haujlwm tuag steel.