France by American Greg LeMond and later on by Briton Chris Boardman, who liked the fact that the system allowed him to shift from his aerobars and his brake levers. The system did not catch on due to technological hurdles. In 2009, Shimano commercially released the Dura-Ace Di2 electronic shifter, and Campagnolo and SRAM followed suit in the early 2010s. As of 2022, the vast majority of top-level professional teams use electronic shifting, as do many amateur riders. Mechanical derailleurs remain popular with amateur racers and recreational riders for cost reasons. Groupset manufacturers have gradually increased the number of gears on racing bicycles, allowing a greater range between the highest and lowest gears while maintaining relatively small gaps between each successive gear. As of 2022, most racing bicycles used in professional racing have 2 front chainrings and 11 or 12 gears on the rear cassette. Carbon fiber has also become more popular for components. Shimano, Campagnolo and SRAM have introduced carbon fiber for their high-end shifters and brake levers, cranks, and parts of their derailleurs. Carbon fiber stems, handlebars, shoe soles, forks and seatposts are also more commonplace, including integrated stem/handlebar combinations. The advantages of carbon fiber are low weight as well as increased vibration damping leading to a more comfortable ride. As of 2022, the majority of professional teams use hydraulic disc brakes for most or all races. A few top-level professional teams still use bikes with caliper brakes in mountain stages, as their disc-brake models are significantly heavier than the UCI's legal minimum weight of 6.8kg. Disc brakes offer better stopping performance, particularly in wet conditions. For many years, racing bicycles were required to use caliper brakes by UCI regulation, but manufacturers began producing road bikes with disc brakes for recreational use in the mid-2010s, and their use was trialled in professional racing in 2016 and 2017. Rider disquiet over the crash safety of disc brakes led to the introduction of versions with chamfered edges to reduce the risk of the rotating disc acting as a cutting blade. In 2018, the UCI concluded the trial and legalised the use of disc brakes in all road racing events. Non-competitive uses Road bicycles are built for casual recreational use, often labeled as "sportif" bicycles or "dropped-bar fitness bikes". These have much in common with a competitive racing bicycle, but the frame geometry is relaxed to make the bicycle more comfortable