Manufacturer:- www.surefire.com
Retailer:- www.lighthound.com
UK Distributor :- www.edgar-brothers.co.uk
Purchase Price :- $250 £148 http://www.xe.com/ucc/
Size:- 155mm (6.13 Inches) long, Body Diameter 26.83mm (1.056Inch), Head 37.34mm (1.47Inch) Diameter
Weight (With Batteries):- 5 3/4oz. 166g
Battery Type / Qty :- 2off CR123 Primary or 1off 18650 Rechargeable Lithium-Ion or PILA 168S
Battery Life :- 1 to 40 Hours (Manufacturers figures)
LED Type :- 5W Luxeon V
Rated Output:- 2-80 Lumens (Manufacturers figures)
Estimated LED Lifespan:- Over 1,000 Hours
Colour:- White
Reflector Type :- Custom Surefire Aluminium
Lens Material :- Pyrex Glass
Electronics:- Controlled power output 6 different levels. Regulated for constant output.
Body Material :- Aerospace Grade Aluminium Alloy
Colour :- Anodised Black Type III
Features:- Lockout Tailcap, Water Resistant, Multi Voltage/battery types.
Accessories :- Stainless Steel Pocket Clip
Guarantee :- Lifetime (No quibble, If it breaks we fix it!)

I have waited a little while before getting one of these. They have been on the market for over a year and initially my interest was in other products. This is currently the pinnacle of Surefire's LED range of torches and sets out to provide all things to all people. A tall order!

The torch is similar in size to a Surefire 6P with a KL3 head, so a compact 2 cell 6V flashlight. But the U2 is a little bit special compared with other surefire lights and this is apparent by some extra features on the head of the light. More on this later...

The body is made in typical Surefire style from aerospace grade aluminium alloy. The machining is about as good as it gets in the flashlight world with detailed design features on all areas. This is no simple plain tube design. It looks and feels professionally engineered.

The knurling on Surefire lights tends to be reasonably rugged and gives the owner a good grip on the lights body. This is at the expense of the owners clothing. The torch will wear it out if constantly removed from tight fitting pockets. I think a good belt pouch would be the best way to carry this light.

The light is comprised of three main components parts. The LED head / electronic assembly. The battery tube body and the tailcap.

Lets start with the tailcap and move forwards.

The U2 tailcap switch performs a couple of functions. First of all it can be removed from the light to give access to the battery compartment. This allows the CR123 cells to be changed. Larger cell types have to be changed by unscrewing the head of the light. More on these in a bit. The tailcap can also lock out the operation of the light. To do this just unscrew it about a half turn from the fully screwed in position.

Normal operation is by pressing the rubber switch. This can be partly depressed for brief illumination. Or it can be pressed in all the way until is clicks and the light will latch on. Pressing the button again will unlatch the switch and turn off the light.

The battery tube is slight unusual in this light. Normally Surefire lights are designed for CR123 3V cells and nothing else fits. Well it looks like somebody was thinking of the many people that want to use alternative rechargeable cells when they designed this light. The tube is larger in diameter and will comfortably accommodate an single 18650 Lithium-Ion Cell. Fantastic so now we can use this light on guilt free rechargeable power.

The body of the light also contains a stainless steel pocket clip. This gives head down carry and also doubles as a handy stand for the light when resting on a table top. Makes taking nice photographs far easier!

Both ends of the body have O-rings which seals the light from dust and damp. I think the light is rated as waterproof, but it's not a dive light. These should be kept lubricated with silicone or another non O-ring damaging alternative. I believe Surefire use Nyogel products for this and the 779ZC and the 759G (Conductive) grease are the ones to use.

Moving on the the head of the light we get to the really interesting bit. I hope. The U2 has a unique method of adjusting the power to the LED. Just behind the reflector assembly there is an injection molded plastic ring. Turning this ring clockwise when holding the light pointing away from you will increase the brightness of the LED. Turning the opposite way will reduce the brightness.

The power adjustment is simple and easy. The only complaint is that you need the light to be on to see it change levels. But you can always set lowest or highest power before turning the light on. Not many lights you can do that on!

There are 6 different levels to the adjustment and I measured the output at each one on my LM631 Light meter as follows.

Level 1 - 80 Lux @ 1m
Level 2 - 170 Lux @ 1m
Level 3 - 320 Lux @ 1m
Level 4 - 623 Lux @ 1m
Level 5 - 1070 Lux @ 1m
Level 6 - 1722 Lux @ 1m

This gives an excellent range of light output and makes the light useful for reading a book or looking into the darkness of the garden to see what's making all the noise!

Runtimes at these levels are estimated and with the help of the people at CPF and there own independent testing will be somewhere near the following. This is assuming the use of two new CR123 primary cells. Runtimes on 18650 and PILA cells will be somewhat less than these.

Level 1 - 48 hours
Level 2 - 22 hours
Level 3 - 11 hours
Level 4 - 5 hours
Level 5 - 2 hours 20 minutes
Level 6 - 1 hour (About 40 minutes of constant light then tailing off to around 50% of max to 60Min)

The power adjustment system uses some sort of hall effect sensor to detect the position of the bezel ring. This means that the head can stay sealed and water tight and no annoying grit will get into the works.

The electronics also have a very good regulation to ensure that the light output remains as constant as possible at each power setting. This delivers the same light level even as the battery voltage drops, or due to the use of a lower voltage rechargeable cell such as a PILA or 18650.

The front of the light contains the same reflector as the Surefire L5 and a Pyrex Glass lens. Glass is not as durable as Lexan to impact damage. But it does resist scratching far better and also has better light transmission properties. Always remember Surefire's product guarantee 'If it breaks we fix it' and you will be fine.

The very front of the light has five small curved cutouts. These allow light to escape when the torch is placed face down on a flat surface. Thus you can see you have left it switched on and take the appropriate action.

Now I think we need a few comments on the light output for this device. I know people will want comparisons with the Night Ops Gladius and this is understandable as they are both variable power high output LED torches. But I think the U2 is designed to fit into a different market than the Gladius.

The U2 has a Lumileds Luxeon V Led and this is rated to give up to 80 Lumens of output. The early Surefire specs listed this as 100 Lumens and this has been downgraded to 80. I don't know if this is the result of Surefire's policy of under estimating all their power ratings / runtimes. Or the fact they realised that LED variations caused some of their products to be under the 100 Lumen figure?

It does not matter as I would guess that only a light meter could actually detect the difference of these two levels.

The light output from a Luxeon V LED is normally considered to be wider than a Luxeon III for a good reason. The size of the Luxeon V surface area is far greater than the Luxeon III as it is made up from 4 led chips. This gives torch designers a headache as the larger light source needs a larger reflector design than the Lux III to produce the same amount of tight focus. This is one of the reasons why the head on the Surefire L6 is so large.

The U2 produces a tighter focus of light than the L4 which also uses a Luxeon V LED. But it is not as tight as the Night Ops Gladius even though the head and reflector size is greater. The Gladius uses a Luxeon III which is why this is the case.

So as you will see from the light meter readings above the Lux readings are lower on the U2. Not to worry though as the U2 produces a more even and less tightly focused beam. On the highest setting it is more a wall of light although it still throws a considerable distance. This is far better for walking around at night of for indoor activities. The overall light output would be an interesting thing to compare but you need an integrating sphere for that.

Just compare the Gladius and U2 beamshots and you instantly see the difference. Pick the one that suits your task the best. Or if your flashaholic needs get the better of you buy both. :-)