Surefire KL4 Differences?

I have 2 Surefire KL4 Led heads. One on a L4 and the other on a Scout weapon light.
Also have a EL1 Outdoorsman.Got to playing around and put Kl4 off the Scout on the 1 cell Outdoorsman and it worked fine.Then put the KL4 off the L4 on it and nothing happened.Swapped the Scout back on and again it worked.
What would be the difference between the 2 heads?
(They both work on their original hosts)
Thanks in advance
Chip

Sounds like you have one of each version. The OLD KL4 (etched KL4) used the Lux-V and could work on low voltages. The newer KL4 (etched KL4A, IIRC?) uses a Seoul Emitter, and will not work on the low voltages that the old KL4 would. Putting the old KL4 on an E1x body (E1e/E1L, etc.) was known as the "TW4" back in the day, and it also allows you to use RCR-123's when used in a 1 cell body. You get about 40 minutes of guilt free flood light! Hope this answers your questions! Oh, and welcome to CPF, BTW!

Thanks for the info and the welcome.
Do you know the difference between the 2 as in Lumens ,run times?
When was the change made?
Chip

The KL4 (and the later "KL4A") were only ever designed to be powered by two-SF123A batteries.
The fact that some KL4 bezels would run on a single SF123A at reduced output and runtime is more a fluke, but one some people enjoyed. They affectionately called the E1e+KL4 combination "TW4" (which is not SureFire nomenclature)

I believe the KL4 was rated at 100 lumens whereas the KL4A was rated at 120 lumens.

Is there a chance of damaging it running it on only 1 cell?

Chippp1961 said:

Is there a chance of damaging it running it on only 1 cell?

Click to expand...

Nope...it never hurts under powering an LED...in fact, you can greatly extend the life of the LED...incans on the other hand...