A pressure regulator for regulating the pressure of a fluid from an associated pressure reservoir includes a regulator body housing a shuttle assembly and supporting a multiplicity of radially-distributed service lobes. Each service lobe includes features in fluid communication with one or more chambers within the regular body, and performs a particular function relating to the pressure and contents within those chambers. Such lobes may include one or more of a bias lobe for regulating pressure within the shuttle bias chamber, a fill lobe through which the reservoir may be filled, a gauge lobe which displays the pressure within the reservoir, and a relief lobe including one or more burst disks to relieve over pressurization in the reservoir or output chamber of the regulator. Each service lobe may slideably engage a respective interface on the regulator body, and be releasably secured there by way of a threaded retainer.