The 425 is the flagship model having been designed for the most common new construction dryer exhaust configuration. While there are a few exceptions, it is primarily used for venting upward in 2 X 6 walls. Where wall depth is restricted, it can be installed in a 2 X 4 wall with a 1" furring strip. The only time the 425 should be rotated is to support pedestal or stacked units for downward venting. This model was designed to allow room for other mechanical components in the cell of the wall. It is narrow enough to share plumbing or electrical runs.