Our Black Strain Reliefs grip the lamp cord where it enters the socket and removes the strain from your wire connection. Our strain-relief bushing is a two-piece design with prongs on one end which clamp down onto the cord as you tighten the narrowing cap over the top, gripping the cord tightly, thus removing the strain from your wiring connection. The most common application is the lamp cord that supports a socket or pendant lamp. Any external force on the cord would tug on the base of the strain relief, and not the cord connection within the lamp. There work with all of our 18/2 & 18/3 cloth covered wire.