Specialty Recreation 18" x 30" White Skylight Inner Garnish

The 'rough opening' is the framed hole or cutout in your RV wall, floor, or ceiling where something like a window, door, vent, or appliance will be installed. It's usually a little bigger than the actual item so there's room to fit and secure it properly. If you're replacing or adding something, you'll want to measure the rough opening—not just the outside of the part—to make sure it fits.