While on a project site the electrician installed backboxes with extension rings however with the additional wall covering the receptacle when installed flush is not completely recessed into the raised cover plate? Someone indicated that the code allows this seperation between the receptacle and the raised cover / mud ring as long as it does not exceed 1/4"? After further research I could not find anyting to reference this, it appears the receptacle when installed is "exposed" between the gypboard and the device raised cover plate / mud ring of apporx. 1/4" is this typical or accpetable my suggestion was a box extender? Is there anywhere in the code that permits this type of installation?