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Cold Harbour Supply

Cold Harbour CHAD-31A (L3 PVS-31A; GPNVG-18)

Cold Harbour CHAD-31A (L3 PVS-31A; GPNVG-18)

Regular price $77.00 USD
Regular price Sale price $77.00 USD
Sale Sold out


*Sold individually. For a full set of PVS-31A, buy two. For GPNVG-18, buy four.

Developed at the request of professional end-users and building upon the success of the CHAD, the Cold Harbour CHAD-31A (Cold Harbour Aperture Defender) is a lens protector for adjustable iris diaphragms that can be used for the L3 PVS-31A and GPNVG-18 and allows users to see objects at all distances with perfect clarity and focus without needing to refocus the objective lens of their NVG. The CHAD-31A comes with an adjustable iris aperture that is specifically designed to fit only L3 PVS-31A and GPNVG-18.


Polycarbonate Multi-Impact Rated

  1. Provides durable, multi-hit, rugged impact protection;
  2. Over 90% Light Transmission
  3. 10-Year warranty against yellowing and lifetime warranty for breakage

Unlike other market offerings, the CHAD's ANSI-rated polycarbonate lens protects the host diaphragm and night vision device from not only dust and debris, but also high-velocity projectiles from force-on-force applications (airsoft bbs, sim rounds, UTMs), spalling from steel targets, etc, and has a lifetime warranty.

Anti-Reflective US Milspec Glass

  1. Anti-reflective coating 
  2. Sac lens protects NOD from single impacts, scratches and dust
  3. Easy to clean without worry about scratching from debris  
  4. Over 95% Light Transmission

Unlike other glass UV protectors from the market, the Glass CHAD uses a US milspec PVS-14 sac lens that has been optimally coated for light transmission for NVGs and cuts down on reflective elements that plague generic UV lenses. The hardened glass design allows for easy cleaning even in debris filled environments. 


Traditionally, most night vision devices have a large objective lens and aperture size to allow the maximum amount of light into the intensifier. An unwanted byproduct of large aperture size is a shallow depth of field - if the user sets their objective lens focus for infinity, then objects within 20 feet are typically out of focus and blurry. Users typically have to delicately refocus their objective lenses for simple admin tasks (reading maps, adjusting kit, etc) which can be cumbersome, especially on devices with articulating pods. 

The iris diaphragm - originally designed for camera lenses without adjustable apertures - solves the focus issue on NVGs by giving the user the ability to dial in the optimal amount of light into the host NVG to maintain full-focus at all distances. By reducing the amount of light, the depth of field increases and everything comes into focus. Because the CHAD is larger than the NVG's objective lens, at wide-open aperture, there is no signal degradation.

By restricting the amount of light entering the NVG, the adjustable diaphragm also acts as a pseudo gain control for auto-gain NVGs, reducing contrast and giving operators the ability to pick out minute details in high light scenarios and reduce blooming from bright light sources.

The smooth-running, knurled adjustment wheel along the entire circumference allows users the freedom to manipulate the adjustment wheel at any angle, making adjustments a breeze. From fully-open to fully-closed is only 1/4 turn of the wheel. When the diaphragm is fully-closed, the diaphragm size approximates the size of a milspec pin-hole day cap which means you can leave the assembly attached to your night vision device. (We still recommend a fully-closed cap for long-term exposure to light or storage)


The iris diaphragm is tested to work with genuine PVS-31A and GPNVG-18 made by L3 Harris. It will NOT work with replica PVS-31s, PVS-31Ds or PVS-31Cs

Polycarbonate Warranty Info: Unlike other market offerings that use fragile glass lenses, non-user replaceable sacrificial lenses or no lens at all, the CHAD features a precision CNC-machined, high-impact polycarbonate lens (the same as our best-selling NV Optics Defender). It is chemically resistant to paints and adhesives, is UV-coated, has a 92% light transmission rate, and is warrantied for 10 years against yellowing, and for lifetime for breakage. The lens housing is custom-made and is ridged along its circumference to allow users to easily and securely mount and dismount the lens for cleaning, or when ballistic protection is not needed.



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