I have established the general mode of operation of ball bearings. It could be extended to roller bearings but this book is about fluids not mechanical design. There are dozens of configurations for all sorts of applications. The roller bearing is an obvious complement to ball bearings because the potential area of contact of a roller is so much greater that that of a ball. However, roller bearings are much more sensitive to accuracy of alignment than ball bearings. This leads to self-aligning roller bearings with barrel-shaped rollers.