"Crowns the joint" perfectly by distributing the exact amount of compound evenly over the horizontal joint.
I have used Columbia flat boxes for over 20 years. They are built to last. Rugged yet precise construction. Quality parts. Worth every penny. For the 12" box, I prefer the regular box over the Fatboy model. Since the finish coat is very thin, it doesn't require holding as much mud. Since this coat already requires fewer trips to the pump, I think the lighter weight is an advantage.