Since bearings usually receive a lot of frictional resistance that generates heat, lubricants such as oil or grease are used to prevent the seizing or abnormal wear that this frictional heat could otherwise cause. Lubrication-free bushings don't need lubricating oil because the bearing body has a lubricating structure made possible by lubricating oil in the bearing body, or by embedded solid lubricant or the like. Since they don't need lubricating oil, lubrication-free bushings are often used for applications such as precision machinery that makes lubricating oil refilling difficult, and equipment with poor affinity to oil. They also greatly reduce maintenance costs by eliminating the need for regular lubrication and enabling stable operation over long periods. Lubrication-free bushings come in a variety of shapes that can be used for different applications as needed. Examples include straight bushings, collar bushings, flange bushings and housing bushings.