For the full breakdown, see our best 8/3 SO Cable guide.
The cord feeding a welder on a job site takes more abuse in a week than a household extension cord sees in a decade. Figuring out what is a SO cable starts with a scene like that, because these cords exist to move power to equipment that isn’t bolted down.
One detail trips up most buyers: SO is a family of cords, not one exact product. Plain SO and SOW have been largely superseded by SOOW, which is why many catalogs use “SO cable” loosely to mean SOOW.
SO Cable Meaning: What The Letters Stand For
Read the designation left to right and every letter describes part of the build. In SO cable meaning, the letters break down like this:
- S — service cord, the flexible cord family built for equipment that moves.
- O — oil-resistant construction.
- OO — oil-resistant jacket and oil-resistant insulation, both layers.
- W — weather/water resistant, which is what turns SO into SOOW.
That pattern repeats across brands, so a spec sheet’s SOOW letter designations always mean the same thing. Add a J, as in SJOOW, and you’re looking at a “junior” service cord rated for lighter 300-volt duty rather than the full 600-volt service rating.
What’s The Difference Between SO And SOOW?
The practical difference is weather and water resistance.
| Rating | SO Cord | SOOW Cord |
|---|---|---|
| Letter meaning | Service + oil resistant | Service + oil-resistant jacket and insulation + weather/water resistant |
| Voltage rating | 600 V | 600 V |
| Temperature range | -40°C to 90°C | -50°C to 90°C |
| Weather & water protection | Not included in the rating | Built in; suited to temporary outdoor use |
| Conductor options | Multi-conductor, 18 AWG to 2 AWG | 2–4 conductors on standard lines; some product lines run 5–30 conductors |
| Common status | Largely superseded by SOOW | The current standard in most catalogs |
Where Is SO Cable Used?
Use SO cable anywhere portable power has to survive rough conditions, repeated flexing, and oil or moisture. The most common jobs are temporary feeds and equipment that travels with the worker.
- Construction and job sites — temporary power drops for tools, lighting, and generators.
- Industrial and shop use — portable machinery, welders, compressors, and maintenance equipment.
- Stage and event work — lighting rigs and sound systems that get packed up and moved constantly.
One safety limit matters more than the others: SOOW is not rated for direct burial or permanent outdoor installation. If the cord will be buried or left exposed to the elements year-round, you need a cable rated for direct burial instead.
Size is the other half of the buying decision.
FAQs
Is SO cable the same as an extension cord?
Not exactly. A household extension cord is usually built for light or medium duty, often rated for 125 or 250 volts.
Can SOOW cord be used outdoors?
What does the J mean in SJOOW cord?
References & Sources
- Temco Industrial. “SOOW Letter Designations.” Explains what each letter in SO, SOOW, and SJOOW cord names means.