Flair 4x10 vent to a 4x8 register opening

This file will convert your 4x8 ceiling register opening to 4x10. It also has two tabs to insert screws into the register to hold it on and a place to put the screws to attach the vent. I would advise applying some foam around the box to prevent leaks that will cause dust streaks on your ceiling. I didn't put in the screw holes because you may need to adjust the location to fit your application. Predrill the four holes to match the size of your screws, this will typically be 1/8" or #30 drill bit. This will require a 3D printer capable of printing 10 inches wide.