COTI on a PVS-31 or Dual Tube Night Vision: Which Tube, Which Side

Dual tube owners ask the same three questions about a clip on thermal imager. Does it go on one tube or both? Which side? And does putting heat in only one eye actually work? This guide answers all three for the PVS-31 and for dual tube goggles in general, with the fit, the mounting steps, what you see, and what a dual tube plus COTI setup costs.

Does a COTI go on one tube or both?

One. A clip on thermal imager clamps onto the objective lens of a single 1x tube and projects its heat picture into that tube. On a dual tube goggle you put one COTI on one of the two tubes. The other tube stays a plain night vision tube.

That is not a compromise people put up with; it is how clip on thermal is meant to be used on a binocular. You keep night vision in both eyes, with the depth perception and the relaxed two eyed view that are the whole reason to own a dual tube, and you add heat to one eye. Your brain gets the scene from both tubes and the warm targets from one. The supplier of our unit fitted it exactly this way on our PVS-31 PRO: one Jerry-C Pro under one objective.

Where does a COTI sit on a PVS-31?

On our PVS-31 PRO the Jerry-C Pro sits at 6 o'clock, directly under one objective lens. The body of the clip on is about one objective wide and hangs below the tube, and its small projector rises in front of the lower part of that tube's objective lens. It never sits between the two pods: there is no room there, and the projector has to reach the lens it feeds.

Those positions are read from our own photos of the Jerry-C Pro on each goggle. The PVS-14 side of the story is in COTI for PVS-14.

Which side should the COTI go on?

The clamp ring closes the same way on either objective, so the choice is yours. There is no wrong answer, but three things are worth thinking about before you clamp it on:

• Your dominant eye. A common choice is to put the thermal in front of your dominant eye, so the heat cue lands in the eye you naturally lead with. If you do not know which eye that is, our guide on which eye for a PVS-14 has a ten second test that works for a dual tube too.
• Where you reach. The Jerry-C Pro has three buttons on the unit, but it also ships with a wireless remote carrying the same three buttons. With the remote clipped where your hand falls, the side the unit is on matters much less for control.
• How you flip. If your PVS-31 has articulating pods and you sometimes fold one pod up to walk with one eye on night vision, put the clip on on the pod you keep down. When the goggle is flipped up, the Jerry-C Pro goes to sleep on its own, and it switches off after 10 minutes up.

How do you mount a COTI on a PVS-31?

1. Pick the tube. Slide the clamp ring over that tube's objective lens.
2. Turn the ring to set the tension, then press the lever shut, with the clip on interface at 6 o'clock.
3. Slide the Jerry-C Pro onto the ring, power it on and choose Highlight or Outline.

There is no calibration step. The Jerry-C Pro uses an optical overlay, so the heat lines up with the tube image once the ring is closed. Set your dual tube up the usual way first, with your eye spacing right and both pods focused; PVS-31 PRO setup walks through it. Then add the clip on and judge it on something past 30 m, where the overlay lines up best.

Does thermal in one eye really work?

Yes, and it is the standard way clip on thermal is used on a binocular. Both eyes see the night vision scene, so the picture you build in your head has the full tube detail and depth. One eye also sees warm targets marked on top. In Highlight mode a warm body is filled in; in Outline mode only its edges are drawn, so the tube picture behind stays clean. Give yourself a night or two to get used to it, the way you did with night vision itself.

A few things help. Turn the threshold down until only the warmest things stay lit, so the heat does not fight with the scene. Try Outline mode when you need to read the ground around a target. And use Breathing, which pulses the overlay on and off at a speed you set, if you want the heat to remind you where to look rather than sit on top all the time. Every mode is in COTI modes explained.

Dual tube plus COTI or PVS-14 plus COTI?

Both carry the same clip on and show the same heat overlay. The difference is everything around it.

If you spend whole nights moving on foot, the dual tube is the more comfortable way to carry a clip on thermal. If you watch from one spot and want the lowest cost, the PVS-14 does the job.

Will a COTI fit other dual tube goggles?

The clamp ring set that ships with the Jerry-C Pro is made for our PVS-14 and PVS-31 objectives. Other dual tube goggles use a range of housings and objective sizes, so we will not promise a fit we have not seen. If your binocular is not ours, email info@nightoperators.com with the make and model before you order, and we will tell you whether the ring fits.

What does carry over to every dual tube: the clip on goes on one tube, the thermal is 1x so it needs a 1x tube, and it adds about 90 g with its battery to the front of that pod. On a dual tube that is already front heavy, plan your counterweight; the numbers are in dual tube helmet balance. For long nights, the external battery pack (about 10 hours at 22 C) keeps weight off the goggle. Use CR123A 3V lithium cells only, never 16340 rechargeables, which run at 3.7V.

How much is a PVS-31 with a COTI?

The Jerry-C Pro is $2,949 on its own. With any PVS-31 PRO in the same cart, $200 comes off automatically. Here are the kits:

The goggle alone is our PVS-31 PRO, from $3,799.95. If you are weighing a dual tube plus clip on against a goggle with thermal built in, read COTI vs fusion goggles before you decide.

Frequently asked questions

What is a COTI?

A COTI is a clip on thermal imager. On a dual tube it clamps under one objective lens and projects a heat picture into that tube, so warm people and animals stand out while both eyes keep night vision. Our Jerry-C Pro is a 640 x 512 thermal at 1x for $2,949.

How much is a COTI?

Our Jerry-C Pro is $2,949. With any of our PVS-31 PRO goggles in the same cart, $200 comes off, so the PVS-31 PRO 1400-1550 kit is $6,548.95. The US dealer listings we compared for this 640 x 512 class ran $3,577 to $4,475 (read 22 October 2026).

What is the most affordable COTI?

The lowest priced complete 640 x 512 clip on thermal we found was our Jerry-C Pro at $2,949, against US dealer listings of $3,577 to $4,475 read on 22 October 2026. Dual tube owners need only one, on one tube, and it ships with the clamp ring set, remote and battery pack.

What is the best COTI for the money?

For a dual tube, the best value is one 640 x 512 unit at 1x on one tube, with no calibration and everything in the box. The Jerry-C Pro does that at $2,949, under the dealer listings we compared. Warranty is 3 months, up to 12 months with Operator Care.

What is the best COTI for the price?

At $2,949 the Jerry-C Pro gives a PVS-31 owner a 640 x 512 sensor, Highlight and Outline modes, a compass heading, a wireless remote, a battery pack and the clamp ring set. The 640 x 512 US dealer listings we read on 22 October 2026 started at $3,577.

Do I need two COTIs for a dual tube?

No. One clip on thermal on one tube is the normal setup. Both eyes keep night vision for depth and detail, and one eye adds the heat overlay. A second unit would double the cost and the weight on the front of the goggle for very little gain.