The BMD Pillow Blocks Bearing unit is a combination of a radial ball bearing, seal, and a housing of high-grade cast iron or pressed steel, which comes in various shapes. Pillow Blocks usually refers to a housing with an included anti-friction bearing. A Pillow Blocks refers to any mounted bearing where in the mounted shaft is in a parallel plane to the mounting surface, and perpendicular to the center line of the mounting holes, as contrasted with various types of Flange Blocks or Flange Units.