VIVOSUN Quiet Register Booster Fan for 𝟒" 𝐱𝟏𝟎" Holes, Cooling Heating Vent with Intelligent Thermostat Control, 10-Speeds Increase Airflow Booster Fan for Bedroom & Attic, Matte White

Very good product! We use it to pull air from our wood heater in the basement, we have tried a couple of other brands, but they do not rate like this one. Simple to use, very well built, and it moves a lot of air. We do not use it in a vent, but i can see how un-obstructive it would be to the air coming from the HVAC Large opening for the air to pass through, and runs very quietly compared to the others we have. We will be replacing the other brands with this one. :)

This thing works great. Cooling the room better. It looks good too.

I bought this to try and compensate the downstairs office temperature which was always a couple of degrees lower than upstairs. My thinking was that it will blow more hot air in the office and will even things out. I have a home assistant and an ecobee so I was able to track the temperature very precisely over time. The verdict after running it for 10 days and looking at the data is: 1. It restricts the airflow significantly when off 2. To get the airflow back to the same level as an open vent you have to run the fan at around 5-6 out of 10. 3. In order to get positive airflow you need to be running it at max speed when it's really loud 4. When it's running it also cools the air which kinda defeats the purpose of improving heating. My data shows that after installing it and running at 5-6 speed for 10 days the temperature at the office never went to the same levels as it was with just an open vent. It might have worked if I ran it at max speed but it is way too loud. I can see how it may be useful for cooling which is why I am keeping it in case I need it in the summer.

Excellent product makes a difference by pulling in more air from the register. Has variable speeds so you can determine how much heat or cold you want to draw in.

Works like a charm. Cools down the room and it's quiet.