NEMA 5-15 devices are three-wire grounding devices (Hot-Neutral-ground) used for 125V circuits and rated for 120 V maximum, 15 Amps. The Connector is designed for use with 3 conductor cables with a diameter from .300” to .480” (18/3 SJ through 12/3 S).
When making connections, make sure they are secure, properly insulated and there are no stray wire strands outside the terminals.
from Powertronics Connections (TM)