Haum rau kev ua haujlwm nquag, qhib thiab kaw sai thiab maj mam; me me kua kuj; yooj yim qauv, kuj me me ntim, lub teeb yuag, yooj yim txij nkawm; zoo sealing kev ua tau zoo; tsis txwv los ntawm kev taw qhia kev teeb tsa, cov kev taw qhia ntws ntawm qhov nruab nrab tuaj yeem ua tau raws li qhov xav tau; tsis muaj kev vibration, suab nrov tsawg.
