Get STW for outdoor extension cords.

STW. The “J” in SJTW means junior—thinner insulation that’s fine for light indoor use but not built for weather, mud, or being stepped on.

Here’s the quick breakdown:

• S = Service cord (flexible, not fixed wiring)
• T = Thermoplastic (PVC jacket)
• J = Junior (lighter gauge, less durable)
• W = Weather-resistant

An SJTW cord is okay for a string of lights on a dry patio or a temporary lawn tool. But if you’re running a miter saw in the driveway, dragging a cord through wet grass, or leaving it out for a season, get the full STW. No “J.” Thicker jacket, better abrasion resistance, less likely to crack in the cold.

The price difference is usually a few bucks. Not worth saving if the cord splits after one winter.