Product review (5 stars): If you have a noisy dryer, this will likely fix it.
I bought a used front load Kenmore HE4 110 series dryer off Craigslist that was extremely noisy. It made a low rumbling noise that obviously indicated a problem. After a little Googling, I learned it was likely a roller. Then I found this kit for a mere $25. The install took maybe an hour. Someone with more experience could have done it much faster.

The instructions weren't exactly applicable to my dryer, but Youtube videos are widely available for most models. I watched the video a couple times and just kinda winged it. As soon as I got to the rollers at the back of the dryer, I immediately found the problem. One of the rollers was in really bad shape with the inside worn so bad, it didn't sit tightly on it's axle but wobbled to and fro.

This bad boy is super quiet now... and I have peace of mind knowing I replaced belt and pulley included in the kit.