These are mounted bearing units designed to provide support for a rotating shaft with the mounting surface on a parallel line with the shaft axis. Typically, they house a bearing inside a cast iron or pressed steel housing and facilitate ease of installation. They are commonly available from large home improvement retailers and suppliers.
The importance of such units lies in their ability to simplify machinery design and maintenance. By offering a pre-assembled and lubricated bearing solution, they reduce the complexities associated with individual bearing selection and installation. Their widespread availability from major retail outlets ensures accessibility for both professional and DIY applications. Historically, these types of bearings evolved to address the need for reliable and easily replaceable shaft support in industrial machinery.