Measure erect girth, then compare it to the store charts. Mammoth and Dragon publish ranges. Red Tiger does not publish inner diameters. Do not invent millimetres for Red Tiger.
Ring size calculator
Measure the circumference around the thickest part of your erect shaft, then enter it below. Not sure how? Measuring takes about a minute.
Typical range is 4.5 to 5.5 inches (11.4 to 14 cm).
How to measure
- Get fully erect. This is the state the ring has to work in, so it is the state you measure in.
- Wrap a flexible tape measure, a strip of paper, or a shoelace around the thickest part of the shaft. For most men that is the base or just below the head. Snug against the skin, not compressing it.
- Read the circumference in inches. If you used paper or a lace, mark the overlap and measure it flat against a ruler.
- Divide by 3.14 to get the diameter. A 5-inch girth is roughly a 1.6-inch diameter. That is the number rings are specified in.
- Size down slightly from that diameter for a ring that will actually apply tension. How far down depends on the material. A soft stretch ring can start closer to your measured diameter than a rigid one.
The size chart
| Erect girth | Approx. diameter | Recommended | Notes |
|---|---|---|---|
| Under 4.0 in | not listed for Mammoth or Dragon | Red Tiger | Below the Dragon store girth band. Red Tiger is three rings; the store does not publish inner diameters. |
| 4.0 – 4.5 in | store Dragon band starts at 4.0 in girth | The Dragon | Dragon store listing: erect girth 4.0 to 6.75 in. Mammoth store listing starts at 4.5 in. |
| 4.5 – 6.75 in | overlaps both store charts | Mammoth Ring | Both Mammoth (4.5 to 7.75 in) and Dragon (4.0 to 6.75 in) list this overlap. Pick texture (Dragon) or a single smooth ring (Mammoth). |
| 6.75 – 7.75 in | Mammoth store band only | Mammoth Ring | Dragon store listing tops out at 6.75 in girth. Mammoth lists 4.5 to 7.75 in. |
| Over 7.75 in | above the Mammoth store band | Mammoth Ring | Mammoth store copy says above 7.75 in girth is very tight. Do not invent a larger SKU. Contact the store if you need a fit answer. |
Source
Girth bands come from the live Mammoth Ring and Dragon product pages (2026-09-16). They are not independent measurements. Red Tiger still has no published inner diameters.The fit test
Once it is on, run three checks before you go anywhere:
The fingertip test. You should be able to slide a fingertip under the ring with mild resistance. If nothing fits under it, it is too tight. If your finger goes under with room to spare, it is too loose.
The movement test. A correctly sized ring stays where you put it. If it rotates or slides on its own, it is not applying enough pressure to do anything.
The five-minute test. After a few minutes, check for numbness, throbbing, coldness, or a dark, dusky or purple colour change. Any of those means remove it now, and drop a size next time.
Mammoth Force
Mammoth Ring
Stretch silicone ring. Store lists oval inner size 1.5 in and a 2.5x stretch.
4.6 from 15,000+ reviews
Free shipping over $50 • Discreet packaging • Ships from Huntington Beach, CA
Safety limits
Wear it safely
- Thirty minutes maximum. The Mammoth, Dragon and Red Tiger product pages all state this.
- Never wear a ring while sleeping.
- Remove at once on numbness, pain, coldness, or a dark colour change.
- The store does not publish Red Tiger inner diameters. Do not guess millimetres.
- HydraForce is water-based on the store listing. Use water-based lube on silicone rings.
The thirty-minute limit applies to every ring, every time, regardless of how comfortable it feels. Comfort is not the signal. Sustained venous restriction causes tissue damage well before it becomes painful in some men, which is exactly why the time limit exists rather than a “take it off when it hurts” rule.
If you have reduced genital sensation for any reason (diabetic neuropathy, spinal injury, post-surgical nerve changes), the warning signs above are less reliable for you. Talk to a clinician before using a constriction ring.
Getting it on and off
Use lubricant. A small amount inside the ring and on the shaft turns both operations into a smooth roll instead of a drag, and it makes the 30-minute limit easier to respect because removal stops being something you put off.
Roll it on partially erect rather than fully erect. That is easier and it seats better. Roll it off the same way. If it is a struggle, add more lube, and consider that you may be a size down from where you should be.
If you are between bands
Take the larger size first. A slightly loose ring underperforms; a slightly tight ring is a safety issue and a guaranteed abandoned purchase.
If you genuinely do not know, Red Tiger is three graduated rings for $24.99. That is less than most single rings and it removes the guessing entirely. Find the one that fits, then buy the ring you actually want.
Mammoth Force
Red Tiger
Three silicone rings. The store does not publish inner diameters.
4.6 from 15,000+ reviews
Free shipping over $50 • Discreet packaging • Ships from Huntington Beach, CA
What to read next
- How to use a penis ring — the full step-by-step
- How tight should a cock ring be?
- Compare every ring — specs side by side
- The complete penis ring guide