Product review (5 stars): Easy DIY fix!
My dryer was popping at least one of these a year (I finally bought a new dryer and don't have that problem anymore).  The first time I had the local repair man come out and fix it.  It cost about $75.  After I saw how easy it was, I started buying the part locally and doing it myself.  That was about $14.
These work just as well as the locally purchased part and are MUCH cheaper!