I recently got this not-new FourSevens light, the Preon P1 mkIII.  Prometheus Lights (aka Dark Sucks) took up the mantle of Four Sevens recently and so the mkIII has some improvements.  Read on for some testing and thoughts!

Official Specs and Features

Here’s a link to the official product page.


There are three body metals:

Stock photo from the website  Those are: Solid copper, satin nickel, and aluminum.  I believe from time to time a titanium body is offered, too.

Just one emitter option.  There are older versions of the Preon, as well, but I will not cover those here.


The going price for the hard anodized version (seen here) and satin nickel is $50.  Copper is more ($70), and titanium is even more.

Short Review

The Preon P1 mkIII (or “Preon” from now on) is a nicely built little light.  I typically carry and AAA light as a “backup to the backup” light at all times, and while the Preon offers some nice touches, I don’t see it replacing what I usually carry.  Programmability is nice but not something I’ll use past the initial setup.  So I can’t call it a gimmick, but it likely won’t be needed long-term.  It does allow getting the light dialed in right up front, though.

Long Review

The Big Table

FourSevens Preon P1 MkIII
Emitter: Nichia 219c (92+ CRI)
Price in USD at publication time: $50.00
Cell: 1xAAA
Turbo Runtime High Runtime
Switch Type: Mechanical
On-Board Charging? No
Claimed Lumens (lm) 100
Measured Lumens (at 30s) 105 (105% of claim)*
Candela per Lumen 27.1
Claimed Throw (m)
Candela (Calculated) in cd (at 30s) 44lux @ 3.436m = 519cd
Throw (Calculated) (m) 45.6
All my FourSevens 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

  • FourSevens Preon P1 Mk III Flashlight
  • ReCyko AAA NiMH Cell (pictured below)
  • Spare o-rings (2)
  • Manual

Package and Manual

Build Quality and Disassembly

Check out the grooves on the head – exactly opposite of how you need them to be for unscrewing the head.  Almost as if they’re intended to prevent unscrewing the head.

As stated above, the build quality is very good.  I don’t think there’s a single thing that anyone would fault on this light.

The head has only pcb contact pads, which means the light requires a button top cell.  The tail end has a thin springy spring.

The threads on the head end (which is what you’ll remove for cell swaps) are unanodized, and quite long.  They’re triangle cut, too.

The tailcap is also removable, so if you wish to remove the pocket clip, that’s feasible.


Here’s a blow up of the tailcap parts.

Size and Comps

Official Specs:

Length: 3.4 in
Diameter: 0.57 in
Weight (with batteries): 1.0 oz

And just one more comparison I want to bring to your attention.  The Preon beside the Lumintop IYP07 – another AAA light.  There are a bunch of similarities between these two lights, including the ability to use the parts almost interchangeably (!!!).  The reflector is even practically the same.  There are two major differences.  First, the switch on the Lumintop is metal.  This also allows the light to tailstand somewhat reliably.  And the modes are different, too.  Or are they, really?  It is almost the Config. 5 option of the Preon….

Retention and Carry

The pocket clip on the Preon is a fantastic collar clip, with a big shoulder and a wide mouth.  Very easy to use, and easy to get over pockets and the like.  It’s also a finished clip, which means the edges are not sharp at all.

The clip is not reversible:  despite fitting on the head end, the light will not operate in this configuration.

There are no other included means for carrying the light.  Since the clip isn’t reversible, the light can not be used as a hatlight.

Power and Runtime

Here’s the cell that wasn’t pictured above.  It’s a ReCyko brande 850mAh NiMH AAA sized cell.  A cell is included.  Prometheus requires NiMH cells to be used.  Primaries might work but use of primary cells voids the warranty (Dark Sucks takes use of NiMH cells seriously!)

As stated above, it’s a button top, and button tops are required.

Here are a couple of runtimes.  I have my light set up on the HML mode group (more on mode groups later) and this also does allow a “Burst” mode (higher than High).  Note that this “High” runtime is just that – it’s not the Burst mode output, which does meet the claimed specification of “100+ lumens.”

Here’s a runtime on Medium.

Neither output really demonstrates LVP, but the output drops so low that it’d be hard to not notice.

Modes and Currents

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps
Burst 100+ 1h 105 0.95
High 60 1.2h 67 0.54
Medium 15 5h 18 0.14
Low 1 45h 0.02

Pulse Width Modulation

Not really any PWM to be seen, but there is some form of… modulation here.  I don’t think it’s visible.

This is different timescales of the LOW output:

And also different timescales of Medium output:

For reference, here’s a baseline shot, with all the room lights off and almost nothing hitting the sensor.  And here’s the worst PWM light I have ever owned.  Also one of the very first lights I ordered directly from China!

User Interface and Operation

The Preon uses a forward mechanical clicky on the tail for operation.

The switch cover is proud, and won’t allow tailstanding.

One thing Prometheus added in this new version of the Preon is a selectable UI – there are 6 possible configurations, as follows:

I believe the light ships in Config. 4 and that’s what I’ve been using, anyway.  But be aware there are options!

Switching through the options is not hard but will probably take some practice.  Press (don’t click) the switch 10x and on the 10th you’ll hold it down (but again, not click).  The light will flash the number of the config it’s in – if you’re in config 4, it’ll flash 4x.  It’ll keep flashing the count as long as you keep holding the switch – for me that’s flashing 4x and pausing for a few seconds, then flashing 4x again.

To switch configs, power cycle once while it’s blinking out the current config.  So for me, while it’s blinking 4x, I press (not click) the button.  This advances to the next config.  Since I’ve now done it and the light is in config 5, and I want it back to 4, I’ll have to cycle through all the groups to get back to 4.  But I can do it all in one config step – one power cycle to get to 6, one more to get to 1, and so on.  Entering the configuration mode isn’t required to switch multiple steps.

Note that actual clicking almost everywhere above that says “press” would technically work, but the physical limitation of clicking makes it less suitable.

Here’s a UI table for Config. 4!

State Action Result
Off Press Hybrid memory* (excluding Burst)
Off (or “Any” really) Double tap Burst
Off Click Hybrid memory* (excluding Burst)
On Click Off
Off Repeated taps Mode advance (Hybrid Memory > Low > Medium > High)
Off Press 10x Configuration mode
  • Hybrid Memory: The last used mode is memorized, but the next mode will be the first mode of the configuration.  So for me (Config. 4 #forlife) if I turn the light off in a “High” state, it’ll come back on in High but the next mode will be low.  If your memorized mode is Low then the next tap will get to Medium (ie Hybrid memory doesn’t do its normal action if you leave the light in Low).

It’s possible I’ve missed something about the UI here and if I did, I apologize.

LED and Beam

In the Preon is a Nichia 219c, and the 92+ CRI variety.  There’s a tiny reflector, with an orange peel texture.

These beamshots are always with the following settings:  f8, ISO100, 0.3s shutter, and manual 5000K exposure.  Low Med High – I’ll try to fill in Burst mode asap (forgot it!)

Tint vs BLF-348 (Killzone 219b version)

Test light is on the left!

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


What I like

  • Build quality is good
  • Config. options are nice (but ultimately… not all that useful)
  • Uses Nichia 219c
  • Uses high CRI emitter
  • Excellent that it includes the ReCyko NiMH cell

What I don’t like

  • Hybrid memory
  • Proud tail switch cover prevents tailstanding
  • Too expensive compared to very similar models (a la Lumintop IYP07)


  • This light was provided by me for review. I was not paid to write this review.  I purchased this light with my own money!
  • This content originally appeared at zeroair.org.  Please visit there for the best experience!
  • For flashlight related patches, stickers, and gear, head over to PhotonPhreaks, another site where I write!
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