SureFire U2 Digital Ultra, retail $270.00 (
Manufactured by SureFire (
Last updated 05-12-09

SureFire is well-known for making the toughest and brightest personal and tactical lights in the world, and the new U2 will not disappoint you.

The U2 has a 5 watt Luxeon Star LED and a stippled (textured) reflector to make its light, feeds from two CR123A lithium camera batteries, has a pushbutton on the tail for both momentary and constant-on functions, and most importantly, has a selector ring on the barrel to select any one of six intensity levels. The LED and reflector are protected by a slightly domed pyrex glass window (or "lens" if you are more comfortable with that term, even though it does not focus or defocus the light in any manner).

The U2 is rated to produce 100 lumens on its brightest setting; however I am not equipped to measure light in lumens - you need an expensive instrument called an integrating sphere to do that, and I do not own or have access to one of these devices.


The U2 comes with batteries already installed, so you'll be ready to roll right away. If necessary, turn the tailcap clockwise (as if tightening it) to disengage the LOTC (Lock Out TailCap) function.

For momentary light any time, press lightly on the tailcap button (but not so hard it clicks) and hold it that way for as long as you need light. Release the tailcap button to turn your U2 back off.

For continuous mode, press the tailcap button more firmly until it clicks, and then release it. The U2 will come on and stay on without any further intervention from you. To turn the U2 off, press the tailcap button firmly until it clicks again, and then release it.

To adjust the intensity, aim the flashlight forward, and rotate the intensity adjustment ring near the front of the barrel counterclockwise to dim, or clockwise to brighten. This ring turns smoothly, without detents (a clicking sensation with a tactile stop at each setting); this ring is totally silent, so you won't give your position away if you're using the U2 in a tactical environment.

The U2 features a LOTC to prevent the flashlight from turning itself on when packed in a box, bag, camping kit, etc. Unscrew the tailcap 1 turn to engage the LOTC (on the sample I'm testing, 1/4th of a turn from fully tightened does the trick), and tighten it back up when you're ready to use your U2 again.

The U2 can be held overhand (like a police officer usually holds his or her flashlight), or underhand (like how most other people hold a flashlight). When held in an overhand grip, your fingers curl around the barrel, and your thumb automatically falls over the tailcap switch.

You can also use the U2 with a pistol, as the LED inside won't blow up when the gun recoils (kicks) every time it is fired. I'm no firearms expert, and I don't even own a gun, so I cannot show you with pictures how the flashlight would be used with a gun.

Photograph of the side of the U2, showing the inscription.

To change the batteries in your U2, unscrew the bezel, throw it in the {vulgar term for toilet}, and flush it away...O WAIT, THAT'S THE GOOD PART!!! So just set it aside instead.

Tip the two dead 123A cells out of the barrel, and dispose of or recycle them as you see fit.

Insert two new 123A cells in the barrel, flat-end (-) negative going in first - facing the tailcap of the flashlight.

Screw the bezel back on, finger-firm tightness only.
Aren't you glad you didn't flush away that bezel now?

The instructional material reads that the batteries should be changed by unscrewing and removing the tailcap, but that did not work with the evaluation sample. Breech-feeding the U2 (by removing the bezel) worked fine here.
Actually, tail-feeding the U2 really DOES work - if you vigorously shake the flashlight up and down with the tailcap off, the batteries will come out, and you can then load two new ones in button-end (+) positive first and then screw the tailcap back on.

Current measurements are as follows (from lowest to highest)


All measurements were taken on my DMM's 4A scale.

Picture of the business-end of the U2, showing the LED emitter, the textured reflector, and the lightly scalloped bezel.

The U2 is extremely well-made and engineered. The same SureFire quality you've come to expect from their personal and tactical lights is built into this product. The exterior finish is a black type 3 hard anodize ("HA-III" as us flashaholics know it), and there's a gold colored material (Chemcoat) inside the barrel to protect it against corrosion from water or bad battery juice.

One of the things I noticed quickly is that the U2 has a lightly "scalloped" bezel, so if the light is set face-down while it's burning (well, LEDs don't "burn", they just emit light, but you get the idea), some light still escapes and you can easily tell it's still turned on, even if you set it down on a completely flat surface like a tabletop or countertop. No more ruined and wasted batteries from your setting the light down and not realising it's still on.
(Yes, I really did that - to a SureFire KL2 if I remember right!)

When the tailcap was removed, the flashlight was relieved of its batteries, and that dreadful suction test was performed, the flashlight held a vaccume (vacum, vaccuume, vaccumn, vaccuummnne, vacuum, etc.), so I believe it is both weather- and water-resistant. I also took the bezel (head) off and performed the same test, with the same results. Even when the button was clicked, there was no air leakage. So you need not be concerned at all about using the U2 in rain or snow, and water landings will not kill it either.

I smacked the U2 against the corner of a concrete stair ten times (five against the side of the bezel, and five on the side of the barrel/tailcap) and was not able to damage the flashlight in any manner, other than causing some rather minor scuffs on the sides of the bezel and tailcap where it was struck. No mechanical, optical, or electrical malfunctions were detected.

Here is a photograph showing the "damage" on the side of the bezel where it was struck.
Would I really try to beat up a perfectly good $270.00 flashlight?
You bet your sugar-coated toilet muscle (sweet patootie) I would, if it's in the name of science.

I tried to cut through the U2 with the blade of a Swiss army knife, and was not successful.
Would I really try to cut up a brand spanken new flashlight?
You bet your sweet patootie (sugar-coated toilet muscle) I would, if it's in the name of science.

There is knurling (texturising) along the barrel and on the tailcap, and some ribbing on the intensity adjustment ring itself; these help aid in retention (the ability to hold the flashlight when your hands are cold, oily or wet). You can use it with the Rogers/SureFire technique or the Harries technique. But remember, I don't own a gun, so I cannot show you with pictures what these grips look like.

The switch has a nice clicky feeling to it; solid yet easy to use. This switch requires roughly the same amount of pressure to activate and deactivate that the switches on the L5 and L6 Digital Lumamax do.
It's firm, but it's not at all difficult to use.

The U2 has a stiff stainless steel clip with a plastic or nylon gripping piece on the end. This piece has a clearance of approximately 1mm to 2mm between the piece itself and the U2's barrel.

This clip *MIGHT* be removeable without tools and without damaging the flashlight; however I cannot verify this with absolute, positive, 100% certainty.

The beam this sample produces is a pure white in color, with none of that obnoxious purple, blue, yellow, or "rotten cat urnie green" tint anywhere in it. Not in the hotspot, and not in the corona.
The beam does have a slight "doughnut" configuration to it, in that the center of the hotspot is slighly dimmer than the edges of the hotspot, however this is not objectionable unless you only shine flashlights at blank white walls. This is a perfectly normal characteristic of a 5W Luxeon LED and reflector combination, and is nothing whatsoever to be concerned about.

Beam photograph (highest setting) at ~12".
Brightness measurements are:


All measurements were taken with a Meterman LM631 light meter.
That slight brownish color was created by the camera; a more accurate rendition is directly below.

The reflector is textured, giving a very smooth beam to the U2.

Beam photograph (lowest setting) at ~12".

Spectrographic plot
Spectrographic analysis of the LED in this flashlight (lowest setting).

Spectrographic plot
Spectrographic analysis of the LED in this flashlight (highest setting).

Spectrographic plot
Same as above; newer spectrometer software & settings used (lowest setting).

Spectrographic plot
Same as above; newer spectrometer software & settings used (highest setting).
USB2000 spectrometer graciously donated by P.L.

ProMetric analysis
Beam cross-sectional analysis.
Image made using the ProMetric System by Radiant Imaging.

Beam photograph at ~15 feet.
That red star thing is from an American DJ Laser Widow.

Sample was sent by PK of SureFire, and was received on 03-30-05.

Product was made in the United States. A product's country of origin really does matter to some people, which is why I published it on this web page.

UPDATE: 04-29-05
SureFire has confirmed that all current SureFire lights should be waterproof to about 33 feet/10 meters. Some evaluations were posted before Surefire made the affirmation that their lights were watertight to 1 atmosphere depth. Any new SureFire lights you purchase now should be considered waterproof to 33' (10M).

UPDATE: 05-02-05
I just repeated "The Smack Test" on the U2 using a steel pipe instead of the corner of a concrete stair. There is some very minor denting on the side of the bezel where it was struck, but the finish was not removed.
No optical or electrical malfunctions were detected.

UPDATE: 12-24-05
I let the visiting nurse use the U2 last night so she could observe my housemate's legs; the product flickers rapidly to let you know the batteries need changing. She asked me "why did it just get a little dimmer?" and handed it to me. Once I saw the flickering, I knew exactly what it was. Changing the batteries restored proper operation.

UPDATE: 01-31-06
I used the U2 for a short time today to provide light for the telephony repairman this afternoon. I know this isn't much of an update; but I used the U2 for this job and that's that.

UPDATE: 02-10-06
I used the U2 this evening to light my brief trip up the side of the house to bring my housemate's powerchair back inside after he called the meat wagon to cart him off to the hospital. It functioned very well for this task.

UPDATE: 03-05-06
I used the U2 this evening to allow the EMTs to see where to insert an IV into my housemate's arm after I called Medic One on Paul's request (he thinks he might have been having a heart attack). As above, it functioned very nicely for this task.
As a positive thought, I looked at the screen on the EKG, and saw normal sinus rythm - Paul's ticker appears to be fine.

UPDATE: 06-17-06
I used the U2 to light up the area under the kitchen sink so that the plumber could see what he was doing.
No problems were encountered, and the plumber thanked me for providing the light.

Tough and durable construction like all SureFire products
Pyrex end-lens to resist scratches, not acrylic or other plastic
Brightness selector ring emits no sound when rotated
Adjustable brightness
Insanely bright at its higher settings

Slight anodizing color mismatch - however this is normal with HA-III process and will not figure into my rating
Very slight doughnut configuration to beam - however this is normal with a Luxeon V and reflector combination and will not figure into my rating

    PRODUCT TYPE: Adjustable brightness tactical handheld flashlight
    LAMP TYPE: 5 watt Luxeon LED
    No. OF LAMPS: 1
    BEAM TYPE: Wide spot with dimmer corona
    SWITCH TYPE: Tailcap click on/off/momentary
    BEZEL: Lightly scalloped; pyrex glass window protects LED and reflector
    BATTERY: 2 ea. CR123A cells
    CURRENT CONSUMPTION: 32mA to 1,374mA
    ACCESSORIES: 2 CR123A cells, wrist lanyard
    SIZE: 6.13" long, 1.48" diameter
    WEIGHT: 5.7 oz.
    WARRANTY: Lifetime, except batteries


    Star Rating

SureFire U2 Digital Ultra *

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