I want to buy a killflash (ARD) for my Steiner T-536 prism scope, but I don't understand how to read the specs on the ones I see online. The scope lives on my AR15. Sure would appreciate some help.

There are some internal threads at the objective lens end, that look like that's where I'll have to screw in the killflash if I can find one that will fit.

Can't seem to post pics here, so here are the measurements of the threads:
Diameter is 1.588" or 40.32mm depending on if its imperial or metric.
Thread pitch is either 32 tpi or 0.80mm.

I measured the threads and I'm confident that I arrived at accurate measurements. Unfortunately I don't know if the threads are imperial or metric, so I gave both here.
Can anyone help me find a killflash that will fit my scope?

Have you tried contacting Steiner?

I would be surprised if it wasn't the same thread pattern as other 5x36 prisms. Honestly, I'd just buy the killflash for 5x36 from Primary Arms or Burris and give it a try.

Not going to tell you what to do but kill flash or the objective lens screens have huge downsides with not much upside unless you are doing serious counter sniper missions where a glint will cost you your life.  The downsides is the optics becomes very unclear with everything taking on a smokey fuzzy look, ruins light gathering of the optic because you are in a sense getting almost only polarized light that can make it through the screen, and all in all they are just virtually useless.  My 2¢ save your money and time.  Otherwise good luck and contact Steiner they may be able to direct you to the correct part.  Another option is cut a small window into a a flip cap you will not sacrifice nearly as much light that way.

I would call EuroOptic
They carry the T-536.

https://www.eurooptic.com/Steiner-Prism-Scopes.aspx

if there is no threading in the front there is no way to add one unless you make one in a slip on way like taking a flip cap and cannibalis it and make a Frankenstein.

Steiner was the first ones I contacted since I'm so pleased with the optic itself. Prism scopes are perfect for my old astigmatic eyes. Steiner emailed me back saying they don't make a killflash and they don't know what to recommend, and I should look at third-party suppliers. But as I mentioned, I don't understand what the specs mean on the supplier's website. For example, Tenebraex has one called "Tenebraex killFlash ARD for 40mm Leupold 40LTCC-ARD". What does the 40mm refer to?
My scope definitely has some unused internal threads in front of the objective lens - those are the threads I measured and reported in my original post. But obviously I'd have to pick a killflash with a matching thread pattern - but I can't choose if I don't know what a given killflash's thread pattern is! I'm hoping to learn something here.

Interesting point - since I'm new to using a killflash (I'm NOT new to AR15's or prismatic scopes), your point makes sense and I hadn't considered it. Actually I have a 1x prism scope by Swampfox that came with a killflash and I've noticed it gives my sight picture a somewhat darker look, but not unmanageable. That's why I was interested in trying one on my 5x Steiner.

I contacted Steiner before I posted here... and they were no help. Basically said "good luck".

I like the idea of a small window in a flip cap. Sounds like it would work, even if it would almost obliterate my field of view!

Good idea - I had forgotten about Euro Optic. I'll be calling them tomorrow.

There is threading in the front. It's either 1.588" I.D. x 32tpi or 40.32mm I.D. x 0.80mm (the two are equivalent, one is just imperial measurement and the other is metric).

Its the size (diameter) of the objective end of the scope (where the light comes in).  That is the end you don't look through.
When a scope is listed as 3x9x40, its 3-9 power with a 40mm objective.
Your Steiner is a T-536.  5 power, 36mm objective

If you look here, there is a bunch for various objectives (but none specifically for 36mm)

Tenebraex KF @ EuroOptic

Now, there is a Leupold Mark 4 Tenebraex Anti-Reflection Honycomb Filter - 36mm, NSN-1010-01-568-9146
listed at OpticsPlanet, so we know it exists.

I think you should hit up support at Tenebraex.  I get the feeling you will be able to find a slip over (like a lens cap), but not a screw in, unless the Leo fits.


If all those fail, you can always get one made by Jon Aadland (of Aadmount).

I was asking him about covers for scopes not listed, "Do I need to send the scope?"
He said no, just get us good measurements.
He is now making killflashes integrated into a sunshade with a front cover.

ARD For 50mm Scopes, 2.280"

Attached File

Ignore the fact his inventory says out of stock.  He builds when ordered, and to order.  
And lifetime warranty.  I dropped a scope on the cap release mechanism, it broke, emailed with photos, and got a replacement a few weeks later.

I would try the Burris first.  They are corporate siblings with Steiner and made their own version.  

https://www.amazon.com/Burris-626004-Anti-Reflection-Device/dp/B00794LHBG?ref_=d6k_applink_bb_dls_failed&th=1&psc=1

I had one on a 50mm objective scope that should gather tons of light and it was always distorted hazyish dark look.  I took it off and have not used it since.  The scope cap you can start small and expand the size till you get to where the obstruction is minimal or use a rectangular cut to reduce the top and bottom view.  God help you if you get dust or crap in the killflash.

Thanks for that, good information. Especially about Aadmount.

Thanks much. That one looks as though it might work for me. Didn't know about the relationship between Burris & Steiner.
It's cheap enough I could afford to not care if it doesn't fit perfectly.

Or just tell Amazon it didn't work and send it back.

If you actually have the need for eliminating lens glare/glint then the best killflash option is three easy steps away...
Step 1: Go buy some pantyhose (or take a pair from your wife/girlfriend)
Step 2: Cut to size with a pair of scissors
Step 3: Stretch over the objective side and secure with rubber bands

Make sure to keep some spare pantyhose cutouts in a small ziplock bag along with a handful of rubberbands

Advantages:
Low cost & effective, fits any type/make of optic you'll come across, quick/easy field replacement when lost or dirty
(speaking of dirt, they don't get easily clogged with mud/dirt/snow like the standard craptastic killflashes)

Disadvantages:
Slight loss of clarity & brightness
(Typically less than issued/commercial "killflashes")

Good idea, thanks for that. The Burris 36mm killflash won't fit my Steiner (I called them on the phone) and Steiner doesn't seem to be willing to help. That's okay - I was never very serious about "needing" a killflash, I just thought finding one would be simpler that it's turning out to be. No big deal... the pantyhose idea is a workable solution.

Not just a workable solution, but arguably the best killflash solution...
Here's a few anecdotal tidbits with that "tacticool appeal to authority" that forums tend to love so much;

Preferred over the issued/commercial killflash by RTC instructors

Preferred over the issued/commercial killflash by plenty of experienced "B4" HOG's

Multiple SR teams used'em on optics while operating deep inside Iraq prior to the launch of the ground invasion