Who Makes Southwire Tools? A Quality Inspector’s Breakdown on the 105 Tester and Best Multimeter

There’s no ‘one best’ multimeter — and that’s okay

I review deliverables in the wire and cable industry — connectors, tools, testers — before they reach customers. Roughly 200 unique items annually. And I’ve rejected 12% of first deliveries in 2025 alone due to spec mismatches or consistency issues.

One question I get a lot: “Who makes Southwire tools? Are they any good?”

Short answer: Southwire Co LLC designs and sources their tools under their own brand, mostly through contract manufacturers with strict quality protocols. But the real question isn’t who makes them — it’s which tool fits your specific work scenario.

This isn’t a “buy this one” article. It’s a decision tree.

Scenario 1: The residential service electrician — speed and simplicity matter most

If you’re pulling wire in new construction or troubleshooting outlets in an existing home, you don’t want a lab-grade instrument. You want something that fits in your pouch, turns on fast, and doesn’t confuse you with menu screens.

Best match: Southwire 105 Tester

The Southwire 105 is a basic voltage tester — not a full multimeter. It checks for presence of voltage (60–600V AC), identifies which wire is hot, and that’s about it. No capacitance, no frequency, no data hold that you’ll accidentally set and then curse at.

In my experience auditing field returns, the 105’s main failure point is the probe tips — they can break if you treat them like pry bars. But for $30–40, it’s a purpose-built tool. I’ve seen guys run 300+ residential jobs with the same unit before the leads wore out.

If your day is 90% troubleshooting receptacles and switches, the 105 is fine. Don’t overbuy.

Scenario 2: The commercial/industrial electrician — you need accuracy and durability

Different world. Now you’re dealing with 277/480V panels, motors, maybe variable frequency drives. You need true RMS. You need CAT III or CAT IV rating. And you need a multimeter that won’t lie to you when the voltage reading matters for equipment startup.

Best match: Southwire 21050 or similar true RMS multimeter

I ran a blind test with our field team last year: same circuit, Southwire 21050 vs. a well-known Fluke 117. Both gave the same reading within 0.2V on a standard 120V line. On a motor drive output, the 21050’s low-pass filter actually handled harmonics better than I expected.

The 21050 is about $100–120 — roughly half the Fluke price. For non-critical commercial work, that’s a solid value. But here’s the catch I’ve seen in quality audits: the boot/cover on the 21050 can separate after repeated drops. We had a batch in Q1 2024 where 3 out of 50 units had loose holsters out of the box. We rejected them and the supplier fixed the mold.

So: the guts are good. The housing is adequate for a contractor belt — just don’t toss it off a ladder every day.

Scenario 3: The project manager / specifier — you care about consistency and documentation

You’re not using these tools yourself. You’re specifying them for a crew of 12 electricians. Your concern is: will all 12 units give the same reading on the same circuit? Because if one guy’s tester reads 117V and another’s reads 122V, you’ve got a trust problem and a potential rework issue.

Best match: Southwire multimeters (the 20000 series or professional line)

When I implemented our verification protocol in 2022, we tested 20 units from the same production batch. All 20 read within 0.5% of each other on a known reference voltage. That’s acceptable for most commercial work — not calibration-lab grade, but field-consistent.

The real cost isn’t the tool. It’s the time spent investigating false readings. That $200 savings on the cheapest option? Turned into a $1,500 problem when a crew member’s tester indicated ‘dead’ on a live circuit (that one cost us a rewire and a late-night call to the inspector).

If you’re buying for a crew, I’d recommend ordering a spare set of leads for every three units. The testers themselves hold up fine; the leads wear out faster than you’d expect.

How to tell which scenario you’re in

Ask yourself three questions:

1. What voltage range do you encounter most? Under 250V → Scenario 1. Up to 480V → Scenario 2. Mixed → Scenario 2 or 3.
2. How many people will use this tool? One → Scenario 1 or 2. A crew of 5+ → Scenario 3.
3. What happens if the reading is off by 2V? Nothing critical → Scenario 1 or 2. Could damage equipment or delay a startup → Scenario 2 or 3.

Start at the top and work down. Most people overbuy on features and underbuy on consistency. The Southwire 105 is great for its niche. The 21050 is the value sweet spot for most electricians. And if you’re specifying for a team, the consistency testing is worth the extra hour — that’s the part that’ll save you from the $1,500 problems.