We use a USA made louvers made by "Salem Vents" and sold by MILLSUPLAY
Hingeless Steel 2-Way Vent | Mill Supply, Inc.
They look like this with 3 positions vents (backwards), closed (waterproof) and Air receiver (Forward)
Hingeless Steel 2-Way Vent | Mill Supply, Inc.
They look like this with 3 positions vents (backwards), closed (waterproof) and Air receiver (Forward)