A regulator (1) having a casing (10) with at least one bore (11) therein. A piston (12) slidably located within the bore (11) to delimit first (13) and second (14) chambers. The first (13) and second (14) chambers being separated from one another by a valve (15) carried on the piston (12) and actuated by a push rod (16). Valve (15) include first (151) and second (152) balls which have different diameters and are mounted in line with respect to corresponding first (155) and second (156) seats. First (153) and second (154) springs act on and urge the first (151) and second (152) balls toward the first (155) and second (156) seats. Fluid pressure from a source (2) being presented to the first (13) chamber and acting on the piston (12) to initially move the second (152) ball into engagement with the push rod (16) and move the second (152) ball off the second seat (156) and thereafter move the first (151) ball into engagement with the second (152) ball and off the first (155) seat to allow fluid pressure to be communicated to the second (14) chamber by flowing past the first (155) and second (156) seats for distribution to a brake system (3).