The Hoyme Back Draft Damper comes in two styles.Both are spring return and as a result can be mounted in any position.
 
The first one pictured below is an inset Butterfly type. Which commonly comes in sizes of 4-6" in diameter.
Contact the factory if other sizing is required.


 

The other type that Hoyme offers is a single blade type regular inline style pictured below. These dampers typically range from 4 - 24" in diameter.
Contact Factory if other sizing is required.






In addition there is also the BDH - Back Draft Hood available in sping close and gravity close models and your choice of regular or painted white metal.