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Picking your Perfect Co-Witness Sights

Picking your Perfect Co-Witness Sights

Whether it’s Costa Ludus, Optics Ready Stealth, or Suppressor Height, Night Fision has sights that work well with most pistol/optics combination. Once you determine whether you want a very low co-witness, a lower 1/3, or an absolute co-witness, its time to shop for sights that accomplish that.

With the large variety of after-market slides available for Glocks and now more frequently Sig Sauer P320’s, we at Night Fision see a variety of depths to which there is a cut, or mill, into the slide for the optic. Because the depth is not universal, it’s important to measure how deep down off the topline, or top-strap, the cut goes. Knowing your milling depth is one of three measurements that help you better shop for the perfect sights. Some business will let you know to what depth they mill for optic cuts if you’re sending your slide to be cut.

Top: A Sig Sauer P320 style slide with a Sig Romeo optic directly mounted to the slide. Above: A Sig Sauer P320 slide with a Leupold Delta Point Pro optic mounted with a slim adaptor plate. 

The next element isn’t always present, but can influence how high your optic sits: a plate. Just like the myriad of slide options there are a number of plates on the market to help better mount your optic to your slide of choice. A thicker slide will push your optic higher up, and thinner plate (such as a sealing plate) will effect the height the optic is pushed upwards less. Many reputable plate manufacturers can accurately tell you the thickness of your plate.

Finally, the most obvious element? The optic. As optics become more common, more companies are producing pistol optics. The section of the optic you should measure is the rear section, which for most optics is where the battery is housed.

Above: A few of the most popular optics we hear being paired with our sights. Swampfox Sential, Trijicon RMR, Holosun 507c, and Leupold Delta Point Pro. 

While the battery housing is fairly similar in height on the Holosun and Trijicon optics, the Leupold Delta Point Pro has more height in the back. If you have a Delta Point Pro, it’s generally found that you’ll need Suppressor Height to make it over the tall battery housing at the rear for a co-witness.

So what do you do with all these measurements? Well if you take your Optic height, add in any plate thickness if you have one, and then subtract you milling depth, you should have an approximate number of the height at which you optic sits above the top-strap of your pistol. If you search for blade heights that are *just* over that number, they will more than likely be a low co-witness like our Costa Ludus sights are sitting at. With a number much greater than the optic height sum, it’s likely they will sit similar to Suppressor Height.

This guide is meant to help you better choose your favorite new sights. Arming yourself with information, measurements especially, can greatly help you shop, or help us do our best to suggest an ideal set of sights for your needs.


  1. John Baker

    I recently went thru these exact measuring scenarios with my Glock 43X MOS. I had all my measurements however when referring to Night Fision published dimensions I found I needed more info. You need to give the notch depth not just the notch width. Knowing the height of the sight is nice however knowing if the bottom of the notch clears the Red Dot is just as important.

    In conclusion, for my Glock 43X MOS with Empire TRIGA plate and Holosun HE507K-GR-V2 the Optic Ready sights were the perfect height for this combination.

  2. Dave Brennan

    I have a Gen 4 Non MOS Glock 23 and I want to have a Vortex Venom 3MOA mounted to it. Can you recommend which co- witness night sight and plate that would give me the optimum setup? Thanks for your help



  4. We do! Head to the Optics Ready Stealth page for Sig Sauer and select the taller of the sights offered. We also have photos of your exact combination included on the page for an approximate view of what the cowitness will be!

  5. It’s tough to say which plate you’ll need if you’re having your gun milled. That would be up to the person milling your gun as to whether they mill for a plate or are direct application milling (cutting for the specific optic footprint of your choice). Once you know that, we would bet our new 330-353 size sights might work best, but again, with milling, the cutting depth is sometimes different than OEM MOS cut—which is what we design off of. Best to get your milling done and know whether or not you’ll need a plate or not, then reevaluate.

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