Description:
The L4 uses a 5W Luxeon LED driven by 2×123.
It can also be driven with a Pila 168s cell.
Or even 1×123 with reduced output.

First Impressions:
As with all Surefire products, the L4 impresses you right out of the box, with its good looks and great fit & finish. The scalopse and grooves on the head make it look really nice. I was twice as impressed once I turned it on. This little light produces a wall of light, that can easily light up an entire wall with an even flood of light.

Size/Weight:
The L4 is a great size, it fits nicely in your hand. Large enough to make you feel secure when holding it, yet small enough to clip inside your pocket for EDC (every day carry).
The light is alittle heavier than your typical minimag 2AA light, but its well worth the extra weight, for how well its built.

Grip/Handling:
Surefire has some of the best knurling around. It is quite agressive, yet not rough enough to feel too scratchy. The light can easily be held with wet or muddy hands.

Build Quality:
As stated above, Surefire is known for their attention to build qaulity, no sharp edges, no rough cuts.
The HAIII hard coating protects the light against scratchs and nicks. So the light will stay like new, even after being EDCed in your pocket with keys, coins, etc.

Features:
The L4 is part of Surefires E series of lights. This means that the L4s head can be used with the other E Series bodies. Such as the E1e, a 1×123 body. This makes for a very small light, that still produces a fair amount of light for its size.
The scaloped bezel lets you know if you left the light on, even when you set it face down. This is a nice feature, especially sence the L4 can get very hot if left on for a while.

Output:
The L4 is rated at 60 Lumens.
It produces a very wide spot of light, which smoothly fades into an even wider corona.
This makes it great for close to medium range lighting, especially indoors. The drawback is that it does not have much throw. I find that its mainly useful under 50 feet. Further than that, the beam is so wide that it may be too dim to be truely useful. Though it will still cast a small amount of light even past 30 yards.

Runtime:
Typically 60 minutes on 2×123 cells.

Heat Issues:
Being a small light, with a power 5W LED, the L4 can get very hot.
I do not recommend leaving the light sit while its on. Holding the light in your hand will make it run much cooler. The blood circulating throgh your hand will draw heat way from the light, just like the radiator in your car. The light was ment to run for long periods of time, but I do think that leaving it on while not in your hand, will cuase it to run alittle hotter than it should be, and may shorten the life span of the LED.

Pros:
Excellent fit & finish
Perfect for large room lighting with its large flood beam
Lot of light from a small package

Cons:
Only 60 minute runtime (although that is respectable, given its output and size)
Not suitable for long range lighting, such as large yards and fields.
Can get very hot with constant use.

Conclusion:
If you are looking for a light that is small enough for you to carry in your pocket and able to light up an entire wall in your home, this is the light for you. You cant go wrong with Surefire quality and service.
Great light for in home, garage, camp ground, and other areas that you dont need to see far away.