"BNVD" is an acronym that stands for "Binocular Night Vision Device."
When USSOCOM was looking to replace the AN/PVS-15, they created a solicitation for a BNVD, much like they did with the "SOF Combat Assault Rifle," AKA, the SCAR.
The L3 entry won the competition and was accepted as the AN/PVS-31, and became the "official" BNVD. The BNVDs we (TNVC) sell are the latest variant of the L3Harris BNVD, AKA the AN/PVS-31A (or B or C, but not D.
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Night Vision Devices (then Night Vision Depot) also submitted a goggle for the USSOCOM BNVD competition as a low cost competitor to the L3 goggle, and needless to say, was not accepted. Night Vision Depot/Devices, has, however, continued to use the "BNVD" acronym as the commercial name for their dual tube goggle system, leading to much confusion, as military folks are often accustomed to simply referring to their systems by their "common nomenclature" (i.e., "BNVD" or "SCAR"), rather than by their alpha-numeric designation (AN/PVS-31A or "MK 17 MOD 0").
Other commercial goggles tend to use various other acronyms or nicknames to distinguish themselves to avoid market confusion with the L3 AN/PVS-31 BNVD (e.g., RNVG Ruggedized Night Vision Goggle, DTNVS Dual Tube Night Vision System, etc.).
As for "XLS" or "XLSH," both L3Harris and Elbit Systems of America (ESA) manufacture several grades of image intensifier tubes, ranging from relatively low spec export tubes, commercial spec or "fallout" tubes and/or "blem" (blemished) tubes, and standard MIL-SPEC tubes that meet all the requirements for DoD rated orders (does not necessarily mean that they are military tubes--only that they meet military requirements).
Without getting too far into the weeds every single designation:
Unfilmed MIL-SPEC tubes are generally considered the top of line image intensifier, and is what is used in most current factory L3Harris BNVDs. Unfilmed tubes are only manufactured by L3Harris at this time. Often abbreviated to "UF" or "UWP" (for Unfilmed White Phosphor--Unfilmed Green Phosphor exists as well, but is far less common) or erroneously referred to as "filmless" (which was an ITT term).
ESA generally has three main types of image intensifier:
YH/YG series is their standard, MIL-SPEC image intensifier
SLH/SLG series is their mid-grade commercial spec tube
XLSH series is their lowest-grade commercial spec tube
The SLH and XLSH are what are referred to as "fallout" tubes, in and that for whatever reason, they failed to make the next higher grade in ESA's grading system. Needless to say, cost also goes down with each successive step in grade, meaning that systems built with XLSH tubes tend to be significantly less expensive than those built with L3H UWP tubes or ESA YH/YG tubes.
This does not necessarily mean that XLSH tubes are bad tubes, however, many of them have very impressive performance, however for whatever minor reason failed to make the MIL-SPEC cut, which may or may not be noticeable to most users. However, the XLSH tubes do have a very wide range of "acceptable" performance, ranging from fairly low (below 1400 figure of merit, or FOM) with no maximum ceiling on performance. For vendors/builders, it is generally impossible to guarantee what the performance of any given XLSH tube will be until you have it in hand, you get what you get performance-wise.
Depending on the vendor, they may deal with this in several ways, with some small batch dealers individually setting pricing on systems based on the specific tubes they receive, charging more for higher performing tubes, and less for lower performing tubes.
Other vendors, like Night Goggles have simply settled on what we feel is a reasonable price for the minimum specification of tube that a customer could potentially receive, and charge that same flat rate across all systems using these XLSH fallout tubes, regardless of performance, which has led to what some refer to as the "spec lottery," i.e., you pay the cost and you wait to see what you get, you could get an okay deal (lowest tube performance), a good deal (decent tube performance), or a screaming deal (exceptional tube performance), all for the same cost, and offer a 14 day, no-questions-asked return policy (assuming still in new condition) if you're unhappy with the unit you've received, which, as others have pointed out, should really not have to be specified, however not all vendors offer this, with many selling XLSH tube systems "as is, no returns."
Something to note:
The L3Harris BNVD, as a premium MIL-SPEC system, identical to those purchased by USSOCOM is sold by TNVC.
The NGI XLS goggle systems are sold by Night Goggles, Inc. (NGI), TNVC's sister company, that is more focused on hunting and outdoors recreation than "tactical" and "professional" applications (not that hunters cannot be professional--however when we refer to "armed professionals," we typically mean those going up against adversaries that may shoot back, which, fortunately hogs and coyotes generally haven't learned to do yet).
The NGI XLS series uses standard ESA F9400 (WP MX-10160) and F9415 (WP MX-11769) XLSH tubes, the lack of the "H" is stylistic only, as the four-syllable "XLSH" doesn't roll off the tongue quite as easily as the three-syllable "XLS" and also ending on a nice sibilant, rather than the more hard-edged "H," and the "H" is somewhat redundant, since all of ESA's standard tube grades end in an "H" (YH, SLH, XLSH).
Since the release of the NGI XLS series, others have also adopted the shortened "XLS" nomenclature to refer to systems using XLSH tubes, however there is not usually a difference with most vendors between the "XLS" and "XLSH" nomenclature (I can't speak to everything every vendor does).
Finally, ESA does also have what are referred to as "FOM Tubes," which are separate from the normal YH/SLH/XLSH grading system, and instead are FOM limited to a specific maximum performance spec, e.g., an F9415M18HIU is a:
F (common)
94 (White Phosphor, 98 = Green Phosphor--applies to ESA only, all L3H tubes are 98xx)
15 (EGAC manual gain control extension, 00 = automatic brightness control only)
M18 (Max 1800 FOM, M20 = Max 2000, M22 = Max 2200, etc.--applies to ESA only)
HIU ("xyz" = additional contract identifiers)
~Augee