Derailleurs are the components that guide the chain between the cogs. These usually work by having a cable pull them in one direction, and then relying on spring tension within the derailleur to pull opposite direction. With the rear derailleur made of a series of springs, rough terrain in mountain biking can see this component slap around, often leading to lots of noise and potential of a dropped chain. In recent years ‘clutch’ equipped rear derailleurs have become the standard for intermediate and better mountain bike derailleurs. This clutch creates friction in the cage that the chain runs through, and offers a quieter ride with a greater reduced chance of a dropped chain. New electronic technology sees small servomotors added to some derailleurs, which control the movement. This is known as electronic shifting. Such technology comes at a premium price, but removes risk of mud, water or general wear affecting shift performance. This is because a cable-operated (mechanical) system relies on precise cable tension and cable condition to accurately move the derailleur between gears.