1/4 inch 3-6mm ID STRAIN RELIEF DOME NUT 24644 24653, IP68 PG7 Connector fits a 1/2 Inch Hole.

.26" ID .49" OD Resistant to most chemicals and solvents Meets UL requirements (seal ring dose not) Seal ring guarantees NEMA 4 x and 6 specifications (IP68) Easy installation: push cable through strain relief and tighten dome nut Use minimum size strain relief that fits your cable Ideal for control cabinets, car washes, hot tubs, instrumentation, underground for direct burial and underwater to 300ft