RegMount fits most scuba regulators with a second-stage body diameter of 2 3/8″ to 3 1/8″ (60–80 mm). That covers the majority of recreational second stages on the market. Use the fit checker below for a quick answer, then read on to learn how to measure your own regulator accurately, what to do with unusual shapes, and how to fit RegMount to an octopus.
Will RegMount fit my regulator?
Measure the outside diameter of your second-stage body at its widest point and enter it below. Inches can be typed as decimals (2.75) or fractions (2 3/4).
Pro tip: The number that matters is the diameter of the round second-stage body where the clamp will sit. That’s not the mouthpiece size or the hose fitting. Measure across the widest round part of the housing, behind the purge cover.
How to measure your second stage
You only need a couple of minutes and one of the tools below. Measure two or three times and use the average. Plastic housings are rarely perfectly round.
Method 1: Calipers (most accurate)
Find the clamp zone
Hold the second stage with the mouthpiece toward you. The clamp goes around the round body of the housing. Find the widest round section that isn’t the purge button or the exhaust tee.
Close the jaws gently
Set the caliper jaws across the housing at that point and close them until they just touch. Don’t squeeze, because soft covers will compress and give a reading that’s too small.
Read and repeat
Note the reading in millimeters, rotate the regulator about 90°, and measure again. Use the larger of the two readings.
Method 2: String or paper strip
Wrap the housing
Wrap a non-stretchy string or thin strip of paper once around the second-stage body at the clamp zone, snug but not tight.
Mark and measure
Mark where the string overlaps, lay it flat, and measure the length. That’s the circumference.
Convert to diameter
Divide the circumference by 3.14 (π). For example, a 220 mm circumference ÷ 3.14 ≈ 70 mm diameter, which is comfortably in range. In inches, 8 5/8″ ÷ 3.14 ≈ 2 3/4″.
Method 3: Ruler (quick check)
Set the second stage face down on a table. Stand two books or flat objects against opposite sides of the housing so they touch it, then measure the gap between them with a ruler. It’s less precise, but good enough to tell whether you’re clearly inside the range or near one end.
Inch to millimeter conversion table
Supported range: 2 3/8″–3 1/8″ (60–80 mm). Sizes near either end of the range should fit, but they deserve a careful check. If you measure right at a limit, contact us with your regulator model.
| Diameter (inches) | Diameter (mm) | RegMount fit |
|---|---|---|
| 2″ | 50.8 mm | Out of range (too small) |
| 2 1/8″ | 54.0 mm | Out of range (too small) |
| 2 1/4″ | 57.2 mm | Out of range (too small) |
| 2 3/8″ | 60.3 mm | In range (lower limit) |
| 2 1/2″ | 63.5 mm | In range |
| 2 5/8″ | 66.7 mm | In range |
| 2 3/4″ | 69.9 mm | In range |
| 2 7/8″ | 73.0 mm | In range |
| 3″ | 76.2 mm | In range |
| 3 1/8″ | 79.4 mm | In range (upper limit) |
| 3 1/4″ | 82.6 mm | Out of range (too large) |
| 3 3/8″ | 85.7 mm | Out of range (too large) |
| 3 1/2″ | 88.9 mm | Out of range (too large) |
Unusual regulator shapes
Most second stages are a round “puck” with the exhaust tee below the mouthpiece. Some designs are different, and they need a closer look:
Side-exhaust regulators
Some second stages vent bubbles to the side rather than downward, and some can be configured for left- or right-hand hose routing. The adapter must sit clear of the exhaust and purge on your specific model. Send us a photo and we’ll help you check.
Very compact travel regulators
Ultra-light travel second stages can measure under 60 mm, or have a flattened or oval body. Measure carefully. If you’re under 2 3/8″ or the body isn’t round, check with us before ordering.
Oval or faceted housings
Measure the narrowest and widest dimensions. If both fall in the 60–80 mm range, the band and clamp will usually conform. If they don’t, ask us.
Large-diaphragm or full-face designs
Very large second stages over 80 mm, or regulators built into full-face masks, aren’t a match for the standard clamp.
Fitting RegMount to an octopus (alternate air source)
Many divers move RegMount to their octopus to shoot selfies and buddy shots, or to slip the camera under rock shelves and ledges. If your octo’s second stage falls within the same 60–80 mm range, the same kit will fit. Measure it the same way, since octos are often a different model from your primary.
Safety first: Your octopus is your buddy’s emergency air supply. Anything mounted on it must not delay deployment, block the purge or exhaust, or confuse a buddy in an out-of-air situation. Brief your buddy before the dive, keep the octo in its proper stowed position, and never use it in a way that compromises an air share. Read more in task loading and camera gear.
Still not sure? Ask us
If your measurement lands at the edge of the range, your regulator has an unusual shape, or you just want a second opinion, contact us. Send us the make, model and approximate year of your regulator, your measurement, and if you can, a photo from the front and side. We’ll give you an honest answer. We’d rather tell you RegMount won’t fit than have you order something that doesn’t work.
For a deeper look at second-stage sizing, read Second-stage sizes explained. When you’re ready to install, follow our installation and assembly guide.
Measured and in range?
The RegMount kit fits second stages from 60 to 80 mm and ships free in the U.S.