There are double seals for ball baring unit and it is normally pre-greased for working in the condition of dust, slob and causticity.是什么意思_There are double seals for ball baring unit and it is normally pre-greased for working in the condition of dust, slob and causticity.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句