“Will it fit my regulator?” is the question we hear most often, and it’s a fair one. Second stages come in round, oval and compact designs, with front or side exhausts, hoses on the right or left, and a wide range of mouthpieces. The good news is that one measurement answers most of the fit question. This guide explains what to measure, how to measure it accurately with tools you probably already have, how mouthpiece size and comfort fit in, and what to do if your regulator is near the edge of the range.
Key takeaways
- RegMount fits most scuba regulators with a second-stage body diameter of 2 3/8″–3 1/8″ (60–80 mm).
- Measure the round body of the second stage where the clamp will sit, not the front cover, exhaust tee or mouthpiece.
- No calipers? Measure the circumference with a soft tape or a strip of paper and divide by 3.14.
- The mouthpiece size affects your comfort, not the clamp fit. A worn or poorly fitting mouthpiece can cause jaw fatigue whatever camera you use.
- Within the range, correct installation matters: clamp snug but not overtightened, purge and exhaust unobstructed, camera level.
Anatomy of a second stage: what the clamp grips
Before measuring, it helps to know which part of the regulator you’re looking at.
Housing (body)
The main case that contains the valve and diaphragm. On most regulators it’s roughly cylindrical. RegMount’s clamp goes around this part.
Front cover and purge button
The face of the regulator, with the purge button and openings that let water reach the diaphragm. The mount must never cover or press on it.
Exhaust tee / deflector
Directs exhaled bubbles to the sides, away from your face. On a RegMount setup, the camera sits in front of the exhaust so bubbles don’t pass in front of the lens.
Mouthpiece
A soft silicone piece with bite tabs, usually held on with a cable tie. It sets your comfort, not the clamp fit.
How to measure your second stage
Use either method below. Measure at the widest round part of the housing where the clamp will sit, usually between the front cover and the hose connection. Avoid the exhaust tee, the hose fitting and any adjustment knob.
Method 1: Calipers (most accurate)
Open the jaws across the body
Put the caliper jaws on opposite sides of the housing, square to the body, not at an angle.
Measure in two directions
Take one reading side to side and another top to bottom. Many second stages are slightly oval. Record both numbers.
Compare with the range
If both readings fall between 60 and 80 mm (2 3/8″–3 1/8″), your regulator is within RegMount’s fit range.
Method 2: Soft tape or paper strip (no tools needed)
Wrap around the body
Wrap a sewing tape measure, or a thin strip of paper, once around the housing where the clamp will sit. Keep it flat and snug, not stretched.
Read or mark the circumference
Read the tape where it overlaps, or mark the paper and measure it flat against a ruler.
Divide by 3.14
Diameter = circumference ÷ 3.14. A circumference of 220 mm gives a diameter of about 70 mm, comfortably in range.
Quick circumference-to-diameter reference
| Measured circumference | Approx. diameter | RegMount fit |
|---|---|---|
| 180 mm (7.1″) | 57 mm (2.25″) | Below range |
| 190 mm (7.5″) | 60.5 mm (2.38″) | In range (lower end) |
| 210 mm (8.3″) | 67 mm (2.63″) | In range |
| 230 mm (9.1″) | 73 mm (2.88″) | In range |
| 250 mm (9.8″) | 79.5 mm (3.13″) | In range (upper end) |
| 260 mm (10.2″) | 83 mm (3.25″) | Above range |
In other words, a circumference between about 7.4″ and 9.8″ (188–251 mm) corresponds to the 60–80 mm diameter range. For an interactive check, enter your numbers in the fit checker on our regulator fit guide.
Common measuring mistakes
- Measuring across the front cover. The cover is often wider or narrower than the body behind it, and the clamp doesn’t go there.
- Including the exhaust tee. Wrapping a tape over the exhaust deflector adds several millimeters and can push a regulator that fits into the “too big” range.
- Measuring at an angle. A tape that spirals around the housing reads long. Keep it square to the body.
- Stretching the tape. Soft tapes and paper should be snug and flat, not pulled tight.
- Guessing from the model name. Manufacturers update designs, and two regulators with similar names can have different housings. Measure the one you actually dive.
Pro tip: Measure both your primary and your octopus. They’re often different models or sizes, and many divers later move the RegMount to the octopus for selfies or for poking the camera under ledges. Knowing both measurements now saves guessing later.
Shape matters too: round, oval and compact designs
Diameter is the main factor, but shape affects how the clamp sits.
- Round housings are the simplest. The clamp closes evenly and the camera can be rotated to any angle.
- Slightly oval housings usually work if both caliper readings are in range. Position the clamp so the camera ends up level when the regulator is in your mouth, not level on the table.
- Compact travel and side-exhaust designs sometimes have flat sections, ribs or protrusions where the clamp would go. Check that the clamp and silicone band can sit flat around the body without covering the exhaust or touching the purge.
- Metal-bodied regulators are often fully in range. The silicone band in the kit protects the finish and improves grip.
Don’t force a fit: If the clamp only holds when it’s tightened hard enough to distort the housing, or if it has to sit over the exhaust, purge or front cover, the regulator isn’t a good match. Never modify life-support equipment to make an accessory fit. Ask us, or your regulator technician.
Mouthpiece sizes and why they matter for comfort
The mouthpiece doesn’t affect whether the clamp fits, but it has a big effect on how comfortable your setup is, especially with a camera adding some weight in front of your mouth.
Common mouthpiece types
| Type | Who it suits | Notes |
|---|---|---|
| Standard | Most adults | Fitted to most regulators. Fine for many divers, but bite tabs wear over time. |
| Small / junior | Smaller mouths, many younger divers | Shorter bite tabs and a narrower flange reduce gagging and corner-of-mouth pressure. |
| Ergonomic / orthodontic | Divers with jaw fatigue or a sensitive palate | Wider bite pads and a contoured shape spread the load across more teeth. |
| Moldable (heat-fit) | Long dives, frequent divers, TMJ discomfort | Softened in hot water and molded to your bite. Follow the maker’s instructions carefully. |
Most mouthpieces fit a common second-stage stem size, but not all regulators are identical. Check compatibility with your regulator’s manufacturer or service technician before swapping, and always secure a new mouthpiece with a correctly sized cable tie trimmed flush.
Mouthpiece fatigue vs. camera weight: how to tell the difference
- Sore jaw joint or temples after every dive, with or without the camera: this usually points to the mouthpiece or a clenching habit. Try an ergonomic or moldable mouthpiece and practice holding the regulator gently with your lips.
- Soreness only with the camera mounted: check the camera angle and position, and fit the comfort chin stabilizer so your chin carries part of the load instead of your teeth.
- Regulator pulls to one side: check your hose routing and length before blaming the mount. A hose that’s too short or routed badly pulls on the second stage whatever is attached to it.
- Torn bite tabs or a split flange: replace the mouthpiece. A damaged one can tear further and is a safety issue.
Good to know: Every RegMount kit includes a comfort chin stabilizer for exactly this purpose. If you lose or wear yours out, a replacement chin stabilizer is available separately.
Installation tips for a secure, safe fit
Once you’ve confirmed the measurement, installation is quick. Our step-by-step installation and assembly guide covers the details. The fit-related points:
- Fit the silicone band first. It protects the regulator’s finish and improves grip, especially on smooth or metal housings.
- Snug, not crushed. Tighten the stainless steel clamp until the mount doesn’t rotate under firm hand pressure, then stop. Overtightening can stress plastic housings.
- Use the right tool. The clamp uses a metric nut, not an imperial one. Using the wrong wrench rounds off the nut.
- Level it in your mouth. Set the final angle with the regulator in your mouth in a normal swimming position, not on the bench. Your head tilts forward slightly when you swim horizontally.
- Check the function. Press the purge, breathe the regulator, and make sure nothing covers the exhaust or front cover openings.
As with any accessory on life-support equipment, assembling RegMount on your own regulator is your responsibility. If you aren’t sure, have your dive shop or regulator technician check your setup. If the clamp ever wears out or gets lost, a stainless steel replacement clamp is available.
What if my regulator is outside the range?
If your second stage measures smaller than 60 mm or larger than 80 mm, or its shape doesn’t leave room for the clamp, you still have options.
- Check your other second stage. Your octopus may be in range even if your primary isn’t.
- Contact us with your measurements. Send the regulator make and model plus both caliper readings (or the circumference) to [email protected] or call (850) 356-6770. We’ll give you a straight answer.
- Use the accessory pack. The J-hook adapter, 3M adhesive and universal base clip mount in the accessory pack add more mounting options for your camera and light.
Measured and in range?
If your second stage is between 2 3/8″ and 3 1/8″ (60–80 mm), the RegMount kit includes everything you need: adapter, stainless steel clamp, silicone band and chin stabilizer, with free U.S. shipping.
Regulator second-stage size: FAQ
What size regulator does RegMount fit?
RegMount fits most scuba regulators with a second-stage body diameter between 2 3/8″ and 3 1/8″ (60–80 mm). Measure the round housing where the clamp sits, not the front cover or exhaust.
How do I measure my second stage without calipers?
Wrap a soft tape or a strip of paper once around the housing, measure the circumference, and divide by 3.14. A circumference of roughly 7.4″–9.8″ (188–251 mm) is within RegMount’s range.
Does mouthpiece size affect whether RegMount fits?
No. The clamp attaches to the second-stage body, not the mouthpiece. Mouthpiece size and shape affect comfort, which is why the kit includes a chin stabilizer to reduce jaw load.
Will RegMount scratch or damage my regulator?
The kit includes a protective silicone band that sits between the clamp and the housing. Tighten the clamp only until it’s secure. Overtightening can stress plastic housings. Installing it on your own equipment is your responsibility, so if you’re unsure, have a technician check it.
Can I use RegMount on my octopus instead of my primary?
Yes, if the octopus housing is in the 60–80 mm range. Customers often use it on the octopus for selfies or for looking under ledges. Make sure the octopus still releases from its holder cleanly and works normally for air sharing.
