Thrunite TH20 Pro

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Thrunite TH20 Pro review

ThruNite TH20 Pro specifications

Brand & ModelThruNite TH20 Pro
Flashlight categoryHeadlamp
Max. output760 lumens
Max. beam distance169 meters
Max. beam intensity7,200 cd
Battery config.1x 14500 / AA
Onboard chargingNo (battery has USB-C)
Main modes5
Review publication dateApril 2024

Review intro:

ThruNite has been in operation since 2009 and has put out some very nice flashlights. In fact, my very first “nice” headlamp was a ThruNite TH20 which has served me faithfully for the past 7 ½ years. I feel like ThruNite products sit in a comfortable “in between” segment: they’re not ultra-budget lights that skimp on features, but they usually don’t break the bank either. Overall, they provide a good mix of value and performance.

Up for review today is the brand new TH20 Pro. As one would expect, this certainly is an upgraded version of my tried-and-true headlamp. But it’s not a direct replacement. In fact, if you put the two next to each other, I wouldn’t assume them to both be TH20 variants. A lot has changed. Flashier specs, for sure. But the Pro is an L-shape instead of T-shape, it uses a TIR vs reflector, and the UI is quite different. Because of that, I think there is room for these models to coexist in Thrunite’s lineup.

Getting started with the Thrunite TH20 Pro is a bit different than the usual “just remove the isolation disc” instruction. Thrunite opted to just physically lock-out the TH20 Pro. To get up and going, just twist to tighten the head of the flashlight.

What’s in the package

The Thrunite TH20 Pro came crammed into a tiny brown cardboard box that featured limited branding and designwork on the outside. There’s basically enough to tell you what the box contains, and that’s it. The TH20 Pro came assembled into its head headstrap with the battery inserted. It was surrounded by some foam to keep everything neat, tidy, and protected. All told, the box contained:

  • Thrunite TH20 Pro
  • Headstrap
  • 14500 battery
  • Pocket clip
  • USB-C cable
  • Spare o-rings
  • Manual

Flashlight in use, Build Quality, and Warranty

There are a lot of decisions that go into making sure you get the correct headlamp. Well, the real answer is to have several so that you have one for whatever you’re doing, wherever you’re doing it. That aside, the shape, size/weight, and beam intensity play major factors in selecting such a light.

Want something that isn’t going to bounce around like crazy when you’re jogging? Then you probably want something lighter, like this AA/14500 offering from ThruNite. Going to be fairly still but want longer runtimes? Go with a 21700-based. And then there’s the L-shaped (right-angle) vs T-shaped choice. Right-angle lights are nice because they do double-duty as utility/work lights.

And, as with the case with the ThruNite TH20 Pro, you can install a pocket clip and potentially mount it to a breast pocket to use that way. But if you’re doing up-close tasks, the light coming from a right-angle headlamp can be a bit odd as it’s essentially coming from the side of your head instead of straight-on (as you would get with the original TH20 which is T-shaped). One thing they both have in common (besides the battery format) is that there is a single e-switch mounted on the end of the flashlight. That works just fine, but I do find that end-mounted switches to be a bit more awkward/unnatural to use than their side-mounted counterparts.

When it comes to build quality, I’d say that ThruNite did an excellent job. The fit and finish are great. The machining is smooth and clean-cut. The coating is premium Type III hard-anodized. Both the switch and optic are held in place with stainless steel rings which are nice accent pieces.


  1. 30 Days RETURN/REPLACEMENT: Any item sold by Direct at Amazon Stores can be returned to get refund within 30 days of receipt in new condition(means the intact condition for secondary offering) with all included accessories, manuals, warranty card(if any), and combo items if you don’t like it.
  2. 24 Months REPLACEMENT: Any product(not battery) sold by Direct at Amazon Stores which is found to be defective under normal use and service within 24 months and more than 30 days counting from the date of purchasing with proof of purchase(eg: order ID) can be replaced with new ones.

Lifetime Limited Warranty: For items purchased after 24 months, we will still provide warranty service, but the cost of the parts and freight(both ways) will be paid by the customers.

LED, Lens, Bezel, Beam, and Reflector

The ThruNite TH20 Pro uses a fairly narrow TIR lens, which makes it handy for medium-distance tasks like going for a walk. Between the more narrow beam and L-shape, it wouldn’t be my first choice for up-close tasks like working on a car. For that, I would reach for my original TH20 first.

While ThruNite had no problem mentioning that the original TH20 used a Cree XP-L2 LED, there is no mention on what LED the Pro version is running, aside for calling it a “High Performance LED”. With the LED sitting behind a TIR, it’s nearly impossible to say exactly what it is. On the plus side, ThruNite offers both CW and NW versions. I opted for the NW. Naturally, that sacrifices some output, but is easier on the eyes.

Spectral measurements: 

I used the Opple Light Master to measure the flashlight at 5 meters distance. 

Mode:CCT:CRI Ra:duv
Turbo4737 K64.2+0.0086

Dimensions and its competition


ThruNite TH20 ProMillimetersInches
Length80 mm3.1 in
Head diameter22 mm0.9 in
Body diameter20 mm0.8 in

Dimensions are rounded to the nearest millimeter and the nearest tenth of an Inch.


ThruNite TH20 ProWeight in gramsWeight in oz
Without battery or headstrap:33 g1.2 oz
With battery, no headstrap:54 g1.9 oz

Weight is rounded to the nearest gram and tenth of an Oz.

Flashlight size comparison with its competition:

Group 1: ThruNite TH20, ThruNite TH20 Pro

Group 2: Zebralight SC53c N, ThruNite TH20 Pro, Wurkkos TS10

ThruNite TH20 Pro: User Interface and Driver

Available modes: 

  • Firefly, Low, Medium, High, Turbo

Available blinky modes:

  • SOS

From OFF:

  • Press and hold: Firefly
  • Single click: turn On
  • Double click: Turbo
  • 3 fast clicks: SOS

From ON:

  • Press and hold: change mode (Low > Medium > High)
  • 1 click: turn Off
  • Double click: Turbo
  • 3 fast clicks: SOS

Mode memory:

  • Yes, the “normal” modes (Low, Medium, High) are memorized. 
  • Firefly, Turbo, and SOS are not memorized.


  • To Firefly: press and hold from Off
  • To Turbo: double click (from Off or On)
  • To Strobe: triple click (from Off or On)

Low voltage warning/protection:

  •  When running lithium-ion batteries, there is a low-voltage blink


  •  SOS, which is accessible via a triple click from both Off and On

Lock-out mode: 

  • No electronic lockout, physical lockout is possible


  • On lithium-ion, there appears to be a 32 KHz PWM – way too fast to be noticeable in normal usage

Additional/summary info on the UI: 

  • Overall, this is a very easy-to-use UI
  • One thing I think could be improved is once you’re in Firefly mode, you can’t ramp up into the normal modes. You can click to turn off, or enable Turbo or SOS. Sometimes I like to start off on the lowest mode and progress up from there. It’s not a big deal, but would have been nice.

ThruNite TH20 Pro Charging and batteries

The ThruNite TH20 Pro came with a ThruNite-branded 14500 battery. The battery has a 920 mAh capacity. It features a protection circuit and USB-C charging port. The TH20 Pro is also compatible with AA batteries. I also tried a couple other 14500 batteries: a button-top Shockli and an Epoch that has a slightly raised positive terminal. They both worked great. I wasn’t able to locate a completely flat-top 14500 battery to test with, but I don’t think it would work. The driver-side contact is just an exposed area on the driver; there is no spring or button… essentially providing physical reverse polarity protection.

If you don’t mind the reduced output, the ThruNite TH20 Pro works well with AA batteries. I tried an AC Delco alkaline battery and it worked so-so. Alkaline batteries would be ok in a pinch, but have a lot lower output and a lot lower runtime. You also run the risk of battery leaks when using alkaline. I much prefer NiMH batteries over alkaline. The output is consistently higher than with alkaline, and the runtime is 50% longer… though still a far cry from the lithium-ion runtime and output

Charge typeFitsNo fitCharge time
Battery with onboard USB-CButton-top 14500 and AA (alkaline / NiMH)Flat-top batteries2h 40min

Performance test

Lumen measurements

How Lumens are Measured: Understanding ANSI FL1 Standards How Lumens are Measured: Understanding ANSI FL1 Standards: The ANSI FL1 standards specify that output in lumens should be measured 30 seconds after turning on, as this is the standardized time for measuring brightness according to the industry standard. This is why we focus on this part in our measurements. The ANSI FL1 standards require an ambient temperature of 22 ± 3°C. We record the ambient the ambient temperature to identify potential reasons for any observed discrepancies.

Lux was measured by a UNI-T UT383 BT at 5 meters. Lumens were measured in a homemade lumen tube using a VEML7700 sensor, calibrated with a calibration light provided by 1Lumen. The included 14500 battery was used in the tests.

ModeAmps at startSpecifiedTurn on30 sec.10 min.
Firefly2 mA0.6 lm0.5 lm0.5 lm
Low0.13 A39 lm25 lm25 lm
Med0.33 A100 lm50 lm50 lm50 lm
High0.90 A350 lm284 lm263 lm93 lm
Turbo3.0 A760 lm646 lm586 lm117 lm
Turbo at 3.6V1.4 A494 lm
Turbo with Shockli 14500772 lm702 lm
Turbo with alkaline110 lm102 lm101 lm
Turbo with NiMH115 lm115 lm108 lm

Ambient temperature during testing:

  • 22 °C 

Parasitic drain:

  • 29 µA on lithium-ion

There’s a bit to unpack here. First up, the Turbo test on the included ThruNite battery missed the output specs. I was a bit surprised by that, if I’m being honest. I retested and got similar values. Not satisfied with that, I carefully hooked up the head of the TH20 Pro to a power supply dialed into 4.20 volts. The result? Turn-on lumens clocked in at 822, much better! So it seemed like the battery was the limiting factor. I dropped in a black Shockli 14500 that I’ve had sitting around for several years and it did pretty good, starting out at 772 lumens. So if you’re being picky about getting the absolute highest output for the first few seconds, drop in a higher-output cell. But it’s not a visible difference, and I’d say it’s not worth the effort or cost.

There was another point of strange behavior that I noticed towards the end of my testing. When turning the TH20 Pro on in Low or Medium modes, the output was considerably less than spec. I did some additional testing and noticed higher values as I rotated through modes. This seems like a really weird UI quirk, and I’m not really sure what to make of it.

  • If I turn the flashlight on in Low, output is 25 lumens
  • If I rotate through the modes and come back to Low mode, it puts out 31 lumens (not a visible difference, but measurable and repeatable)
  • If I turn the flashlight on in Medium, output is 50 lumens
  • If I rotate through the modes and come back to Medium mode, it puts out 82 lumens

ThruNite TH20 Pro Battery Life: Runtime graphs

How Runtimes are Measured: Understanding ANSI FL1 Standards About ANSI FL1 runtime standards: The runtime is measured until the light drops to 10% of its initial output (30 seconds after turning on). This does not mean that the flashlight is not usable anymore. The last column shows how long the light actually works till it shuts off. If there is a + symbol, it means that the test was stopped at that particular point, but the light was actually still running. This happens on certain occasions, with certain drivers, firmware, or batteries.

For most of the tests, I used the included ThruNite lithium-ion battery. I wanted to test AA’s as well, so I also used an AC Delco alkaline battery and a Fujitsu (Eneloop) 1900mAh NiMH battery.

ModeSpecifiedRuntime (ANSI FL1)Time till shut off
Moon18 days
Low18h 30min
Med7h 50min6h 19min6h 19min
High6h 20min4h 23min4h 48min
Turbo2h 24min2h 31min4h 7min
Turbo with alkaline50min53min
Turbo with NiMH1h 24min1h 30min

The TH20 Pro’s Turbo runtime was right inline with specs. The rest of the modes, though, came up quite a bit short. I don’t know if that’s related to the odd lumen output behavior that I discussed in the Lumen Measurements section.
As expected, the AA runtimes are considerably shorter than with lithium-ion. With AA showing both reduced output and runtime, it doesn’t make a lot of sense to use AA unless you really desire lower output (eg, for child use) or for backup power when your included lithium-ion battery runs out.

I’ve also included a comparison with a couple of the more recent AA or AA/14500 flashlights I’ve reviewed before: the Zebralight SC53c N (AA only) and the Wuben H5 headlamp (AA/14500). Of the NiMH tests, both the Zebralight and Wuben had twice the output of the ThruNite – and ANSI runtimes aren’t all that different. In comparing the lithium-ion tests of the ThruNite and the Wuben, the ThruNite starts off twice as bright, but that only lasts for about 30 seconds before dropping off a cliff. The Wuben maintains its higher output for much longer, not dropping down at all for the first 10 minutes.

Peak beam intensity and beam distance measurements

About Peak beam intensity: Understanding ANSI FL1 Standards About peak beam intensity The calculated value of distance in meters at which the flashlight produces a light intensity of 0.25 lux. (0.25 lux is about the brightness of a full moon shining on an object). This means that the intensity has decreased so much, it becomes difficult to see darker objects, or objects that don’t reflect light. The columns ‘Meters’ and ‘Yards’ use rounded numbers.

Intensity was measured at 5 meters after being turned on for 30 seconds. A UNI-T UT383 BT lux meter was used.

ModeSpecifiedCandela measured MetersYards
Low450 cd42 m46 yd
Medium950 cd62 m67 yd
High3,025 cd110 m120 yd
Turbo7,200 cd6,450 cd161 m176 yd
Turbo with NiMH1,600 cd80 m87 yd

Ambient temperature:

  • 22 °C 

ThruNite provided only a single intensity spec. I wasn’t able to hit that with the included battery, but given my observations from earlier that the flashlight is capable of higher output with a stronger battery, it’s entirely possible (likely) that the TH20 Pro can hit the claimed intensity.


Camera settings and distance: Beam shots of the building are taken at 10 m (11 yd) using a Canon EOS R100 with a lens set to 18mm. Manual settings: ISO 400, 1/4sec, F4.5, 5000K.

Beamshots of the following flashlights compared:

  • ThruNite TH20 Pro (NW)
  • ThruNite TH20 (NW)
  • Wurkkos TS10 (4000K)
  • Zebralight SC53c N

Please note that the following beamshots are mainly intended to showcase the beam pattern and beam quality, rather than overall performance. These images are typically taken directly after activation, and in different seasons or weather conditions, and therefore do not fully represent its overall performance. For accurate performance metrics, such as output, beam distance, and runtimes, you need to look at the performance section of this review.

Disclaimer: This flashlight was sent to us for review at no cost by ThruNite. We have not been paid to review, nor have we been holding back on problems or defects.

Final Verdict


  1. Good build quality
  2. Full kit with battery, clip, strap, etc
  3. Lightweight
  4. Simple UI
  5. NW and CW choices


  1. Misses lumen and intensity specs with the included battery
  2. AA performance is low compared to other lights
  3. Quirky output in Low & Medium modes

Explanation on star ratings:

1: Avoid: a match would be a better choice – 2: Poor: significant defect or issues; almost unusable – 3: Average: some defects or issues; but still usable 4: Good: recommended (minor issues) – 5: Great: highly recommended

Reviewer Gabriel

3.5 stars: ★★★⋆

While our star rating provides a reliable indicator, we encourage you to read the full review to make an informed decision based on your own needs and preferences.

Some sequels outshine the original, and some fall short. Though, it seems odd to me to call the ThruNite TH20 Pro an update to the TH20 – they are very different in real-world usage. The TH20 Pro is a right-angle light with a narrow TIR, whereas the TH20 has a T-shape and very floody reflector.

For what it is, the ThruNite TH20 Pro is a pretty decent AA/14500 headlamp – it’s nice and lightweight and easy to use. The included USB-C charging battery does hinder performance a little bit, and there’s seemingly a weird UI bug that changes the Low and Medium brightness depending on how you access them. That aside, if you’re in the market for a small, light headlamp for around the yard, trail, or campsite, the ThruNite TH20 Pro is a pretty decent option.

Buy your ThruNite TH20 Pro here

1lumen selects and reviews products personally. We may earn affiliate commissions through our links, which help support our testing.