TerraBloom ECMF-200, Quiet 8" Inline Duct Fan with 0-100% Variable Speed Controller, Air Tight Metal Casing, Energy Efficient EC Motor. HVAC, Growing and Exhaust Applications Blower for Large Spaces

I used this to boost the HVAC to a distant room that was poorly regulated. I removed the base and mounted it between two new end plates in a 8x12 rectangular duct. Tied the power to the fan control thermostat circuit via relay so any time the HVAC was on the aux blower would be also. I really like the speed control, allowed me to get just the right bonus flow to the distant room. It comes with a digital and a potentiometer (rotary) type of controller. I used the digital one. Both retain the setting between power cycles. I have it set to 3 (of 8) and can barely hear the blower, even when right under it.It has about a ~15 foot control cable and 6 foot power cord. it also comes with a short breakout control cable if you want to make your own controller, with a tachometer signal available, which I didn't need or use.My only concern is the 140F max temperature rating of this unit, but I don't think my heater will violate it.

Costs more than Vivisun but this one is built far better than vivosun and very quiet . takes significant amount of time and effort to install if you are installing this in a tight ductwork so better to spend the extra $$ on good quality booster fan that you don't have to touch it again.

The speed is variable to pretty low RPM, and shuts off at the bottom end. The top speed moves a huge amount of air. The decibels are pretty low throughout the range. Quieter than a smaller different brand I bought prior.

I put a conical HEPA filter on the fan to capture dust in the air in my woodworking shop. It appears to be well made, is much more quiet than I expected, and has a variable speed switch. It doesn't appear to heat up after long periods of usage and is light enough to pick up and move around the shop (even with the large filter). It works very well, but in retrospect I would have bought a fan with more CFM because the filter is so thick it reduces the intake airflow by about 25%.Not sure what "Stretch" is as a rating factor.

Set this up and works really well. Got the filter and airflow is great and noise is minimal.