Product review (5 stars): so I would also recommend a good cleaning now and then
New house has what was a woodshop in the basement with a Broan / Nautilus wall vent. It was out of balance for so long it wore out the sleeves in the old motor, so no amount of cleaning / balancing would fix the vibrations that you could feel and hear upstairs when the fan was running. I got one of these and a new fan motor ( # 99080180) and replaced the old set and was back in business. I just had to swap the mounting bracket to the new motor and press the shaft into the fan blade hub by hand until it was seated, reinstalled everything and applied power. No more vibration and way more quiet. I didn't even have to balance the new blades. I had a look at the old motor and blades and the way the shaft mounts in the old blades is different, so I would suggest buying the motor and new blades together and just toss the old ones.

Also, as others elsewhere have noted, sometimes you just have to clean your blades up if they start to vibrate, so I would also recommend a good cleaning now and then, if your blades are out of balance, it will eventually damage the motor sleeves / bearings.

Another thing about safety! You'll see the little plug on the motor, it will fit in a regular US wall outlet. DO NOT PLUG IT IN TO A WALL OUTLET!!!
This thing is meant to be securely mounted inside the wall vent and powered by the little outlet in it. Don't get yourself electrocuted or a finger lopped off by being dumb! It has way more torque than you would expect and can twist right out of your hand when it spools up!