At only 6 grams, the Prime chain catcher prevents the chain from damaging your frame when the chain falls off the rings of your road bike. It may be a simple piece of metal but it could save you a lot of tears and the cost of a new frame. Simply attach it to the front of your derailleur with the supplied bolt, which comes in a matching colour, and hit the roughest roads you want - without fear! The chain catcher is available for double and triple to prevent chain falling from double road CranksetAlloy 6061 Anodized in Red,Gold,Blue,Black and SilverWeight: 6g with 7075 Alu bolt