This is the Titan Fitness Revolving Pull Up System: a rack accessory that helps you take your workouts to the next level. It has room for 4 pull up bars (1.25-inch or 2-inch fat bars). The revolving system is made of steel and black powder coated. You can mount these to T3 or X3 racks. The below video shows what you can do with this:
This rack mounted fitness system measures 46-inches long and 25.25-inches deep.