Surefire X300U: A vs B – Big Tex Outdoors
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Surefire X300U: A vs B

Ike Stephens

Surefire X300U: A vs B

 Ever since Surefire came out with their newest version of the X300U (the B version) there has been quite a bit of confusion as to what the differences are and which is best suited for a particular application. This article will outline the differences and provide some insight as to which would be best for your intended use.


For a limited time the code: Surefire64 will give you any of these lights for $205!

X300U-A on the left & X300U-B on the right



First a little history...

 In 2015 Surefire discontinued the public sale of their popular X300U-A to release the brand new “upgraded" X300U-B model. However since they still had a contract with a government agency to supply them with the older X300U-A model, Surefire decided to make the “A” version available for public purchase again in 2016.



Well that's cool but what's the difference?

Really, there’s not a whole lot. The older versions of the X300U-A (produced prior to 2016 before they were originally discontinued) had an output of 500 lumens. (click here for a great article on lumens) When the X300U-B came out they boosted the lumen output to 600 lumens (another great article is here) while still maintaining the same runtime. Once surefire started making the X300U-A publicly available again they increased its output to 600 lumens as well. 

It’s pretty safe to say that any X300U-A model you purchase from a retailer will be the upgraded 600 lumen version although it may be possible that a few still have some old stock and you may wind up with the lower output 500 lumen version. As time goes on the odds will go down. 
Every X300U-A that we sell is guaranteed to be the 600 lumen version.

It should be noted that Surefire has tens of thousands of boxes created for the old X300U-A (500 lumen output) and are labeled as such. Rather than throw out those old boxes and (money) they have been placing stickers that say “600” over the “500” marking on the box. This applies to both the X300U-B and the new X300U-A versions. It’s no cause for concern, just something to be aware of if your box has a sticker on it. SEE THIS PRESS RELEASE FROM SUREFIRE 


The press release from Surefire regarding the packaging

These pictures show the stickers that you might find on the package.

Mounting System

The only other difference between the two is the mounting system. The X300U-A uses the older style Rail-Lock® Mounting System. which is best suited for polymer framed handguns.

The Rail-Lock Mounting system on the X300U-A-TN

The X300U-B uses the T-Slot Mounting Rail System which is best suited for metal framed handguns as well as AR-15 or similar style rails. The T-Slot system is also used on the X400 series of weapon lights. The main issue that people had been experiencing with the T-Slot style mount on polymer guns is the overtightening of the light causing reliability issues with the gun or under tightening of the light causing the light to come off. The Rail-Lock system is definitely prefered for use on polymer framed handguns but for use on an AR, the T-Slot has some distinct advantages.

The T-Slot Mounting System

An X300U-A with a Unity Tactical EXO Mount


The Rail Lock system (A) on the left and the T-Slot (B) on the right


Activation Paddles

The only other difference is the activation paddles. The original X300U-A have a longer narrower design while the X300U-B and new production X300U-A have a shorter, stubbier paddle. Really the only way to tell if you have the new 600 lumen X300U-A or the old 500 lumen X300U-A is to look at the paddles. There won't be any other markings on the lights themselves that show the lumen output.

The old (500 lumen) X300U-A on the left and the new production (600 lumen) X300U-A on the right.



Holster Compatibility

It should also be noted that some holsters are made for the X300U-A and NOT the X300U-B. It is best to verify with the manufacturer to see if your holster/light combo will work before purchasing.

The Raven Concealment Systems VG3 Holster will work with both versions.

Color options

Right now you can get the X300U-B in any color you want as long as it's black. The X300U-A is available in both FDE and black variants.


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  • Pan on

    Thank you for the great article. I have been carrying and training with my x300 for a few weeks now and I am extremely happy with it. I bought from you guys mainly due to your extremely informative article as well as the fact that you stock only the newer 600 lumen models. Cheers!

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