UL White Book

OUTLET BUSHINGS AND FITTINGS (QCRV)

Quote
GROUNDING
Metal reducing washers are considered suitable for grounding for use in
circuits over and under 250 V and where installed in accordance with
ANSI/NFPA 70, ‘‘National Electrical Code.’’

That's all I have except they make big holes small. [Linked Image]

Bob Badger
Construction & Maintenance Electrician
Massachusetts