Trialsriding consists of hopping and jumping bikes over obstacles, without touching a foot onto the ground. It can be performed either off road or in an urban environment. It requires an excellent sense of balance. The emphasis is placed on techniques of effectively overcoming the obstacles, although street trials (as opposed to competition oriented trials) is much like Street and DJ, where doing tricks with style is the essence. Trials bikes look almost nothing like mountain bikes. They use either 20, 24 or 26 wheels and have very small, low frames, some types without a saddle.