secured to the regulating cylinder 5 a with split pin 4 split pin 4 traverses u notches 32 of the adjustment knob 2 and is affixed within split pin bore 31 adjustment knob 2 is maintained in interlocked relation with bushing 3 under compressive force of compression spring 1 which is captured between a shoulder or rim not shown defined at one end of adjustment knob 2 and split pin 4 spring 1 urges adjustment knob 2 towards bushing 3 to position stops 28 in selected ones of notches 29 29 c to rotatably secure knob 2 in relation to bushing 3 the adjustment knob 2 has a position aperture or indicator 36 that may be selectively aligned with any one of index notches 29 29 c of bushing 3 to provide a visual indication of the selected gas setting of the multi block gas regulator as will be described in further detail below as illustrated in fig5 adjustment knob 2 is positioned forwardly of hand guard 21 a and gas block 6 a such that it is easily accessible to an operator because of the position of adjustment knob 2 and the type of interlocking engagement provided between adjustment knob 2 and bushing 3 single handed manipulation or operation of adjustment knob 2 from either side of hand guard 21 a is easily effected fig6 is a side view of the multi block gas regulator 13 a shown in fig2 illustrating the low profile.