This is a very satisfying device to have on your bike. ......Never needs any attention. It is always prepared to do its job, without so much as a how-do-you-do.
This ChainWatcher is made of nylon and it has a stainless steel worm gear hose clamp inside of it. We have never had a report of one needing to be replaced as long as we have been making them. This device attaches to your seat tube next to your inner chainring and prevents the chain from coming off, on the inside, no matter how out of adjustment your front derailleur is. In fact, it allows you to adjust your derailleur to give a good strong shift in to your inner chainring.