Lumintop PK21-T Flashlight Review

Lumintop PK21-T Flashlight Review

Lumintop added a “T” to the PK21 flashlight – the PK21-T still uses 2 21700 cells and offers a Luminus SFT-40 emitter for an amazing throw.

Official Specs and Features

I can’t find an official listing for the Lumintop PK21-T flashlight at this time. The PK21 is available though, as a very similar comparison.


There’s just this one version of the Lumintop PK21-T flashlight. The PK21, which has a different emitter, is available too. 


I don’t see a price for the PK21-T, but the PK21 is selling for $135.95 at

Short Review

Lumintop really killed it for making a thrower out of the PK21 line. This flashlight claims 1200 meters, and hits it! With these two (included) 21700 cells, the long body makes the light very nice to handle, too. I don’t love how simple the interface is – with the e-switch, I’d really hope for something more than just four modes. 

Long Review

The Big Table

Lumintop PK21-T Flashlight
Emitter: Luminus SFT40
Price in USD at publication time: ?
Cell: 2×21700
Runtime Graphs
LVP? Yes
Switch Type: E-Switch
Quiescent Current (mA): 0.27 (switch lit)
0.02 (switch unlit)
On-Board Charging? No
Claimed Lumens (lm) 1650
Measured Lumens (at 30s) 1651 (100.1% of claim)^
Candela per Lumen 213.8
Claimed Throw (m) 1200
Candela (Calculated) in cd (at 30s) 9400lux @ 6.019m = 340547cd
Throw (Calculated) (m) 1167.1 (97.3% of claim)^
Claimed CCT
Measured CCT Range (K) 6300-6900 Kelvin
Item provided for review by: Lumintop
All my Lumintop reviews!

^ Measurement disclaimer:  I am an amateur flashlight reviewer.  I don’t have $10,000 or even $1,000 worth of testing equipment.  I test output and such in PVC tubes!!  Please consider claims within 10% of what I measure to be perfectly reasonable (accurate, even).

What’s Included

Lumintop PK21-T flashlight what's included

  • Lumintop PK21-T flashlight
  • 21700 (2) button top

This is not a production sample, so you’re likely to get the normal host of Lumintop things with your purchase. 

Package and Manual

Lumintop PK21-T flashlight box

Lumintop PK21-T flashlight box

Lumintop PK21-T flashlight lens cover

Lumintop PK21-T flashlight manual

Build Quality and Disassembly

Lumintop PK21-T flashlight

This is a long boy! The two 21700 cells being in series (and end to end) really make this a nice light to handle. 

Lumintop PK21-T flashlight led centering ring

I might have done this myself, but I did notice that the centering ring for the emitter was dislodged (as you can see above.) This was easy to fix though, as the bezel unscrews easily. I’m nearly sure the light was not like this when I received it but at the point I noticed it I don’t believe I had loosened the bezel. So just check yours when you get it, and be sure the bezel is tight. 

Lumintop PK21-T flashlight led centering ring fixed

The tail has four ceramic glass breaking balls. 

Lumintop PK21-T flashlight tailcap

Also down here is a tripod mounting hole. 

Lumintop PK21-T flashlight tailcap glass breakers

Both the tail and head have nice big springs. The threads on the tail end are anodized and very smooth, too. 

Lumintop PK21-T flashlight tailcap threads and spring

On the head end, though, are unanodized threads. Cell swaps will be better through the tail end because of this.

Lumintop PK21-T flashlight head spring

As stated above, the bezel unscrews easily. 

Lumintop PK21-T flashlight bezel removed and disassembled

Whenever you put yours back together, note that the reflector is keyed! There’s a little divot in the flat part of the reflector there, and that needs to go directly over the screw on the shelf of the body.

Lumintop PK21-T flashlight reflector is keyed

Size and Comps

68mm x 29mm x 251mm and 374g (with cells)

If the flashlight will headstand, I’ll show it here (usually the third photo).  If the flashlight will tailstand, I’ll also show that (usually in the fourth photo).

Lumintop PK21-T flashlight in hand

Lumintop PK21-T flashlight in hand

Lumintop PK21-T flashlight in hand

Here’s the test light with the venerable Convoy S2+.  Mine’s a custom “baked” edition Nichia 219b triple.  A very nice 18650 light.

Lumintop PK21-T flashlight with standard lights

Lumintop PK21-T flashlight with standard lights

Also above is the light beside my custom engraved TorchLAB BOSS 35, an 18350 light.  I reviewed the aluminum version of that light in both 35 and 70 formats.

Retention and Carry

The only way included for carrying the Lumintop PK21-T flashlight in my prototype package is this threaded tripod mount in the tailcap. This seems to be a very specific application of threaded mount, but if you have a good sturdy tripod it’ll probably work fine.

Lumintop PK21-T flashlight tailcap tripod threads

It could also work fine on those handles that have tripod holes. 

Power and Runtime

The driver of the Lumintop PK21-T flashlight requires 8.4V (maximum, 7.4V nominal) to run. That requires two cells in series, and the proper size is 21700. 

Lumintop PK21-T flashlight with 2 21700 cells

The package includes two 21700 cells, and they’re button-top cells. Flat top cells should work fine because the light has springs on both ends IF the cells have enough reveal on the positive end to still make contact with each other (the “series” part) AND the overall length is enough. I measure these Samsung 50G (with added button) at around 72mm, so nearly standard 21700 length.

The cells go into the light in the usual way – positive end (button) toward the head.

Lumintop PK21-T flashlight with 2 21700 cells installed

Below are a few runtime test. Ouptut looks quite good, especially on the High mode, which maintains 900 lumens for well over 3 hours.

Lumintop PK21-T flashlight runtime graph

runtime graph

runtime graph

runtime graph

The light does shut off when the cell voltage is low, at an appropriate 2.7 or 2.8V.

Modes and Currents

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps (@8.4V)
Turbo 1650 12m+3h30m 1651 3.07
High 900 3h50m 938 1.22
Med 350 12h 348 0.36
Low 25 7d 36 0.03

Pulse Width Modulation

Only the lowest mode (left, below) has any squiggles, and this isn’t even PWM. Nothing to worry about here.

For reference, here’s a baseline shot, with all the room lights off and almost nothing hitting the sensor.  Also, here’s the light with the worst PWM I could find.  I’m adding multiple timescales, so it’ll be easier to compare to the test light.  Unfortunately, the PWM on this light is so bad that it doesn’t even work with my normal scale, with is 50 microseconds (50us).  10ms5ms2ms1ms0.5ms0.2ms.  In a display faster than 0.2ms or so, the on/off cycle is more than one screen, so it’d just (very incorrectly) look like a flat line.  I wrote more about this Ultrafire WF-602C flashlight and explained a little about PWM too.

User Interface and Operation

Control of the PK21-T is by way of a single e-switch on the head end. It’s a nice big switch and has the Lumintop logo. The logo is translucent, and behind it is an (or two) indicating emitters.

Lumintop PK21-T flashlight e-switch

Lumintop PK21-T flashlight e-switch profile

Lumintop PK21-T flashlight e-switch actuation

Below you can see the switch lit in blue. I don’t think it lights any color other than blue, and it seems to mostly be for locator purposes and to indicate approximate battery charge. For a few seconds after the light is activated, the switch will blink.

Three blinks: <15% charge
Two blinks: 15%-75% charge
Steady for 2s then off: >75% charge

Lumintop PK21-T flashlight e-switch indicating in blue

Here’s a UI table!

State Action Result
Off Click On (Mode Memory)
On Hold Off
On Click Mode advance (LMHT)
Any Double click Strobe
Strobe Double Click SOS
Strobe or SOS Click Previous mode
Off Click 3x Battery check^
Off Click 7x Iterate switch backlight

^ Battery check blinks out the actual voltage of one cell. I suppose the driver is reading the series voltage (which should be in the range of 5-8.4V) and splitting it to average the cell voltage value. So when the cells (each) are 3.4V, the light will blink 3x then pause and blink 4x. It doesn’t blink 6x then 8x.

LED and Beam

Lumintop has used a Luminus SFT-40 emitter in the PK21-T. The PK21 had a bigger domed emitter, so these two would make a good pair – high output (PK21) and great throw (PK21-T).  This is a domeless emitter.

Lumintop PK21-T flashlight emitter

The reflector, as you can see, is large and smooth.

Lumintop PK21-T flashlight reflector

The bezel looks to be stainless steel and has some shape.

Lumintop PK21-T flashlight strike bezel

Lumintop PK21-T flashlight emitter on

LED Color Report (CRI and CCT)

CRI and CCT are not a surprise for this very throwy light. CCT goes from around 6300 to 6900K and CRI stays around 70. 


These beamshots are always with the following settings:  f8, ISO100, 0.3s shutter, and manual 5000K exposure.

Tint vs BLF-348 ( 219b version) (affiliate link)

I keep the test flashlight on the left, and the BLF-348 reference flashlight on the right.

I compare everything to the 219b BLF-348 because it’s inexpensive and has the best tint!


What I like

  • Fantastic throw
  • Love the runtimes – that flat output is great!
  • Very simple user interface  
  • Package includes cells

What I don’t like

  • Light turns on when tailcap is screwed on
  • Hold for off


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