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Klein Tools

Klein Tools RT210 GFCI Outlet Tester

A three-light plug-in tester for standard and GFCI receptacles that shows common wiring faults and has a button to trip a GFCI.

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Klein Tools RT210 GFCI outlet tester, front view with the wiring-condition chart
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Photo: Klein Tools

Key facts

Outlets
3-wire receptacles, 110/125 V AC at 50/60 Hz
Conditions indicated
Wiring correct, open ground, open neutral, open hot, hot/neutral reversed (reverse polarity), hot/ground reversed
Not indicated (manual)
Quality of ground, multiple hot wires, combinations of defects, and reversed grounded and grounding conductors
GFCI test
Hold the tester's test button for 7 seconds; the GFCI should trip and the lights go dark
Display
Three indicator lights with the key printed on the tester
Safety rating
CAT II 300V
Drop protection
2 m (6.6 ft)

Which version should you buy?

This page covers: RT210 GFCI outlet tester alone.

  • RT210 GFCI outlet tester

    This page

    Model: RT210

    What differs
    Uses indicator lights to show common wiring faults and has a GFCI test button.
    Best for
    Basic outlet wiring and GFCI checks.
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  • RT110 basic outlet tester

    Model: RT110

    What differs
    Checks outlet wiring with indicator lights but has no GFCI test function.
    Best for
    Simple wiring checks when GFCI testing is not needed.

  • RT250 outlet tester with LCD

    Model: RT250

    What differs
    Adds a display of voltage, wiring faults and GFCI trip time.
    Best for
    Reading voltage and how long a GFCI takes to trip.

  • RT200 older GFCI outlet tester

    Model: RT200

    What differs
    Discontinued earlier GFCI tester, rather than the RT210.
    Best for
    Matching an existing RT200 when identifying older stock.

Watch out

  • RT110 has no GFCI test; the AFCI/GFCI model in the related-items list is RT310.
  • RT250 adds an LCD and trip-time readings; RT210 uses indicator lights.
  • RT200 is discontinued; check the model number rather than the similar name.
  • The candidate RT250 + RT210 listing contains two testers, not the RT210 alone.

Why people pick it

  • Checks the six common wiring conditions in seconds
  • Test button confirms a GFCI actually trips
  • Light key printed on the tester, rated for a 2 m drop

Know before you buy

  • Can't judge ground quality or catch a reversed neutral and ground (a bootleg ground), per Klein's manual
  • No voltage reading or trip time; it shows lights only
  • Shows one condition at a time and misses combinations of faults
  • If a test fails, Klein says to consult a qualified electrician

Full specifications

Outlets3-wire receptacles, 110/125 V AC at 50/60 Hz
Conditions indicatedWiring correct, open ground, open neutral, open hot, hot/neutral reversed (reverse polarity), hot/ground reversed
Not indicated (manual)Quality of ground, multiple hot wires, combinations of defects, and reversed grounded and grounding conductors
GFCI testHold the tester's test button for 7 seconds; the GFCI should trip and the lights go dark
DisplayThree indicator lights with the key printed on the tester
Safety ratingCAT II 300V
Drop protection2 m (6.6 ft)

From manufacturer documentation, checked November 2, 2026. Spotted an error? Tell us.

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