Circular gable louvers have no sides. It is just a continuous loop around the vent. Areas portraying too many square and triangle shapes can benefit from the style breakup of a round vent. Taking eyes from the monotony of the basic structure being so plain.
What makes these so inexpensive is the careful thought in the construction of the louvers. Using true .019 aluminum and limiting the width of the vent louvers to their strength ability. Super lightweight construction.
Nope. No corners here. Just a smooth face racing around in circles. Other vents have a crimped, pie crust face. Not so appealing. These round gable louvers have a sleek, smooth face for a more professional look. And yes, flat square metal can be arched and curved.