这台电风扇转动时很安静，因为它使用了优质的滚珠轴承。

This electric fan runs quietly because it uses high-quality ___ball-bearings.

自从换了新的润滑剂后，这个门滑动起来像滚珠轴承一样顺畅。

After applying the new lubricant, the door slides like a ___ball-bearing.