This is not correct. The AN/AVS-9 and AN/AVS-6 are concurrent systems, one does not supersede the other. You're thinking of the older 15mm eyepiece lens assemblies which should pretty much all have been replaced by the newer 25mm eyepiece assemblies, at least on military issued systems. (reposted from an earlier similar thread):

The “newer” (they’re not that new) F4949/4212/4210 25mm ANVIS oculars are functionally identical to PVS-14 oculars, but lack the threaded ring for the eyecup retaining ring, which limits the use of things like eyecups, demist shields, filters, etc. that are usually threaded into the eyepiece assembly or attached to the ring.

AB Night Vision has in the past sold a retrofit threaded ring that can be epoxied in to ANVIS eyepieces.

There is also an accessory attachment ring that can be epoxied on to the objective of the ANVIS objective lens assembly that allows the use of most PVS-14 accessories such as LIFs, sacrificial lenses, daylight covers, compasses, etc.

These accessory rings are also used for AVS-7 HUD, among other things, and are usually installed from the factory on AVS-6 translating objective lenses, but not on most AVS-9s.

The difference between the AVS-6 and AVS-9 is among one of the most misunderstood aspects of the commercial night vision industry, and it’s misunderstood even by many vendors.

First of all—AN/AVS-6 and AN/AVS-9 are only military designations, the “ANVIS” goggle as a system is designated as the F4949, F4212, and F4210 (basically minor variations in lens configurations for fixed wing and rotary wing applications, but essentially all the same basic goggle), and used extensively in the civilian aviation market as well.

The AVS-9 is also not an “upgrade” to the AVS-6 just because it is designated with a bigger number, the AVS-6 and AVS-9 are essentially parallel systems that both continue to be upgraded, moreover, different variants exist for different mount locations based on different aviation helmets, the most common variant being the (v)3 with the center mount.

While there are numerous different models of the ANVIS based on application (usually having to do with lens filters, accessories, etc.) in general the AVS-6 is intended for Army rotary wing use, and usually has the accessory ring attached to a translating objective lens (the lens itself stays put when the objective focus ring is rotated so as not to disturb accessories like HUDs). The AVS-9 is intended for Air Force fixed wing use and usually does not have accessory rings installed, and has a rotational focus lens assembly.

Most commercial aviation ANVIS are the F4949 model - basically the AVS-9, not the AVS-6, however, most surplus parts on the second-hand market tend to be AVS-6 parts.

Meanwhile, the F5050 AN/PVS-23 was a ground goggle that looks a lot like ANVIS systems, but was optimized for ground use, and uses PVS-14 eyepiece assemblies with eyecup retaining rings, and uses AVS-6 STYLE translating objectives with accessory rings, but without the various aviation ("Minus Blue") lens coatings (of which there are several classes) used on aviation goggles.

I say this all because purchasing ANVIS systems and parts on the second hand market can be an even bigger minefield than PVS-14s or other NVDs—the ANVIS system is actually relatively easy to build from parts, and parts are generally fairly easy to find and affordable, but not many people know how complex the ANVIS family is, nor do many garage builders go through all the proper QA/QC steps (such as collimation and properly matching tubes, since they often use “surplus” tubes without data sheets) when building them.

The reality is that most of the “cheap” ANVIS goggles out there are not and have never been aviation certified, nor would they actually qualify for an “AVS-6” or “AVS-9” designation—they were built by a hobbyist in a garage workshop (some organizations will cheaply unload factory built F4949s that have been de-certified for aviation use from time to time, so they’re out there as well).

Buying the “wrong” second-hand ANVIS could mean you get the 15mm eyepiece lens assemblies, you could have mismatched lenses, some guys will just use PVS-14 oculars since they tend to be more plentiful and easier to find than ANVIS oculars unless you’re rebuilding a set, and they may install objective lenses of unknown quantity (you could end up, e.g., with one lens with a Class B filter, and another with a Class C), and this is all without discussing “lobed” versus “circular” objective lens assemblies.

I love ANVIS goggles, they’re some of my favorites to use, and I’ve even considered having my set of AVS-6s re-tubed with some nice UF WP tubes—but more so than perhaps any other system, you need to know what you’re looking at if you’re going to start getting into second-hand parts and systems, and I’ve observed (though I usually try to stay out of them personally) threads in various NV and gear related groups where even fairly high profile vendors whose names get thrown around a lot on social media and the forums have been called out for their inaccurate information and lack of knowledge on ANVIS systems and giving out bad information.

I’m not saying don’t buy ANVIS goggles or look for deals on the second hand market, but honestly, after years of digging through the different variants of ANVIS goggles, and even so, not being what I would call an “expert” on them and the different variants (was never an aviation life support guy, either) I’ve determined the best way to ensure that you’re getting a decent set of ANVIS is to only buy unmolested factory built sets, but this will mean you will have to find and add the eyecup retaining rings and usually accessory rings as well, which is added cost and hassle.

~Augee