Klein Tools MM400 Multimeter, Digital Auto Ranging, AC/DC Voltage, Current, Capacitance, Frequency, Duty-Cycle, Diode, Continuity, Temp 600V

Klein Tools has always set the standard for professional-grade tools, and this multimeter is no exception. From the moment you pick it up, the build quality speaks volumes — rugged, solid, and clearly designed for real-world job site demands.Accuracy is spot on, whether you're measuring voltage, current, resistance, or continuity. The readings are consistent and fast, with virtually no lag, which makes troubleshooting efficient and reliable. The auto-ranging feature works flawlessly and saves time in the field.Durability is another standout. This meter is clearly built to last, with a reinforced casing that can handle drops and daily wear. The display is sharp and easy to read, even in dim lighting, and the controls are intuitively laid out for one-handed use.Packed with features like true RMS, backlit display, and a wide measurement range, it’s everything a professional or serious DIYer needs — without the unnecessary fluff. Klein Tools continues to prove they understand what technicians actually use and value.In short, this meter nails it: fast, accurate, durable, and thoughtfully engineered. If you want a meter you can count on day in and day out, this is it.

I needed a reliable meter to trouble shoot my malfunctioning Samsung refrigerator/freezer.This Klein mm420 features checked all the boxes I needed and more, feels solid and built for serious use.You can look over the specs: 600v, 10amp…. etcbut this CAT III, true root mean square (TRMS) meterexceeds anything (I) a home owner and DIY “electrician” needs.I found a service manual for the Samsung fridge on the weband followed the diagnostic flow chartsmeasuring values from the components directly,off the pc board connectors,and off the main processing board directly.The only meter functions I needed were continuity, dc volts, ohms, and temperature.The meter made selecting the function simpleand the auto range made the readings easy and worry free.I like the back light displayand the readings lock feature allowed me to transfer the values to my notes easily.This method found the problems,I replaced some parts, and the fridge works!To conclude others may contend there are better meters(more accurate, better designed, what ever),but my experience as a novice foundthe Klein mm420 to be an excellent meter at a good price.

Works great, needed it to do temperature read for a clamp on application. My only complaint is that the contrast is pretty weak compared to other multimeters I've used. The response time is better than some of my other ones.

Not bad. Mid-tier capabilities with a great screen. Thinner than most full functional multimeters, side lead jacks allow for thinness, better portability without sacrificing safety or ability to change leads. As capable as my Fluke 117 but 1/3 the price and easier to pack. I would consider this to be the perfect back up to my Klein 810 Pro or for standalone use in a quick troubleshooting scenario. Nit picks include position of lead jacks right where my fingers hold the meter; lack of non-contact voltage sensing and a lack of a work light. Any two of those three would make it a 5/5.

Great product! As described!

This meter is awesome. It is very accurate, even measures temperature. Reasonably good leads too. Not a highly accurate bench meter, but this is great for the hobbyist, and even pro's who don't need extreme accuracy.

I should know to TRUST KLEIN Tools. Extras others require you to upgrade in price. Nice Quality. Love the Hanging MAGNET Strap.

As a diesel tech just starting out, it covers everything you’re gonna need great brand for a good price really can’t beat it. I bought some test leads to go with. It would recommend all alligator clips as well.