A properly adjusted front derailleur will keep your chain on your chainrings in almost all situations. In some cycling disciplines, most notably cyclocross, bicycles are subject to much more jostling and abuse. Riders in these situations often take extra measures to prevent chain drop, usually in the form of a guard attached to the front derailleur or seat tube.
This chain deflector from Far and Near is one of the lightest available. In fact, when you remove the stock steel bolt and concave washer from your front derailleur to install this deflector, the weight penalty is a mere gram. These are manufactured from 7075 aluminum, and aggressively machined without sacrificing functionality. A red anodized bolt and concave washer are included, and the deflector itself is available in four different anodized colors.
Installation of the Far and Near chain deflector will require a T25 Torx wrench. The deflector is installed on the front side of your front derailleur's braze-on mounting tab, in between the supplied bolt and washer. Care must be taken when reinstalling the front derailleur to ensure proper alignment; please consult your front derailleur's mounting instructions for guidance.