The tapped base in these pillow block ball bearings allows the bolts to be threaded up into the bearing from below the surface. They have a smaller footprint than standard pillow block bearings and are useful in applications that have limited space. They have ball bearings which have a small contact surface with the bearing raceway which reduces friction. Low friction allows ball bearings to run at higher speeds but with a lower load capacity than roller bearings. Pillow block bearings allow the shaft to rotate smoothly while the base supports the load.