A rotary steerable system including a steering section having not more than one piston or not more than two pistons in a transverse cross-sectional plane of the steering section. The steering section includes two distribution flow passages each extending from a valve to a piston. A ratio of a distribution flow passage diameter to steering section diameter is at least 0.07. The distribution flow passages are contained within a central area of the steering section, with a ratio of a central area diameter to steering section diameter being 0.5 or less, preferably 0.4 or less. The steering section may include two pistons having center points that are separated by an angle greater than 120 degrees, preferably about 180 degrees. A duration for which only one of the sets of pistons is activated is greater than 110 degrees of rotation of a valve rotor, preferably greater than 150 degrees.