This particular hinge is a ball bearing hinge, which has small ball bearings between the hinge knuckles to reduce friction. Ball bearing hinges increase the life of the hinge, tend to be quieter, and make the door easier to open. The PHG Swing Clear Hinges are usually used for commercial grade or solid doors that are extremely heavy. You may have noticed it looks a little different than most hinges. It’s design is made so that the door is opens a lot wider than a normal day to day door. Lot’s of times you will see them used on handicap accessible doors.