Can I increase or decrease size of vent cap?

[tmy23]

Greetings. Installing a multi-location (toilet/shower) bathroom exhaust system. The manufacturer calls for 4" vent to the fan and 5" out. Having a tough time finding 5" cap that the boss likes. Can find plenty of 4" and 6". Can I reduce to a 4" cap (preferably) or increase to a 6" cap right at the wall outlet? thanks!!!

 

[Standardairconditioner]

Either is fine.

The reduction will have practically zero impact on any fan's cfm.

 

[Sponsor]

 

[Jadnashua]

I'd opt for the larger one. The fan is likely to use slightly less electricity and the flow rate may increase. It's generally not a great idea to use the flexible ducting, either...smooth stuff works better. If it needs to be insulated, they do make insulation designed to slide over the solid vent ducts.