Trail riding or trail biking is a varied and popular non-competitive form of mountain biking on recognized, and often waymarked and graded, trails; unpaved tracks, forest paths, etc. Trails may take the form of single routes or part of a larger complex, known as trail centres. Trail difficulty typically varies from gentle ‘family’ trails (green) through routes with increasingly technical features (blue and red) to those requiring high levels of fitness and skill (black) incorporating demanding ascents with steep technical descents comparable to less extreme downhill routes. As difficulty increases trails incorporate more Technical Trail Features such as berms, rock gardens, uneven surface, drop offs and jumps. The most basic of bike designs can be used for less severe trails, but there are “trail bike” designs which balance climbing ability with good downhill performance, almost always having 120-150mm of travel on a suspension fork, with either a hard tail or a similar travel rear suspension. Many more technical trails are also used as routes for cross country, enduro, and even downhill racing.