The LEVEL5 10-Inch MEGA drywall flat box is a universal mud box that fits into any drywall finisher’s taping tool arsenal. In a 7”/10” flat box combination, a 10-Inch box is used for a second fill coat. In a 10”/12” box combination, the 10-Inch flat box is used for the first fill coat. MEGA boxes hold 25% more joint compound versus standard boxes.