The size listed above is the rough opening dimension (dimension between the studs - not overall size). Overall dimensions for this vent will be larger than the noted measurement above. Please call if you need to order the vent based on overall dimensions, are unsure what you need or if you need a non-traditional vent size/shape. All gable vents are made to order and because of their custom nature are non returnable. Having them made to your specs insures that you will get the exact vent that you need.