Product review (5 stars): Brought my dryer back to life in a couple of hours!
This OEM Whirlpool repair kit fit my dryer perfectly and has returned it to full function.  I saved a bundle doing it myself versus placing a service call, let alone what a whole new dryer would've cost!  On my machine, the idler pulley had seized and eventually the friction of the belt sliding over the pulley caused it to break (but not before the belt wore a deep groove in the pulley!).  If you're comfortable with basic hand tools, you should be able to handle this repair, especially if you review some of the how-to videos on YouTube.  The most tedious part of the job for me was removing the old triangle clips that hold on the pulley and rollers; the clips on my machine had lost their pliability, yet they weren't brittle enough to break them easily.