Road bike tyres may appear similar but there are key differences; tyres are folding or non-folding. Rubber compounds can also differ, with softer compounds offering better grip but a shorter tyre life. Some tyres can offer an additional layer of puncture protection. An important consideration is tyre width – 23mm has long been standard, but wider, higher-volume 25mm and even 28mm tyres are now increasingly preferred. Most road bike tyres are clincher tyres but competitive racers often opt for tubular tyres which are glued onto the wheel. Tubeless tyres are also becoming increasingly common on road bikes but need to be matched to compatible rims.