How to Choose a Tension Ring Size (and When to Try a Different One)

The tension ring is the small part of a vacuum therapy system that does a big job. After the pump creates an erection, the ring moves from the cylinder to the base of the penis and helps keep blood from leaving. A ring that is too loose may not hold the erection. A ring that is tighter than you need is more likely to be uncomfortable.

This guide explains how ring sizes work, the sizes and types we actually carry for Pos-T-Vac and Osbon ErecAid systems, and the signs that it is time to try a different one. If you are wondering which ring is "best," our older article on the best tension rings for a vacuum therapy pump covers that. This one is about fit.

The basic rule: start with the largest ring that works

MedlinePlus, from the U.S. National Library of Medicine, gives simple advice: if your device comes with bands in different sizes, use the largest possible to maintain an erection (MedlinePlus). The ring guidance on our product pages says the same thing: start with the largest comfortable inside diameter, and size down only if you need to.

In practice, that means:

  1. Begin with a larger or softer ring from the set that came with your system.
  2. If it holds the erection comfortably, you have found your size.
  3. If the erection fades too quickly with the ring in place, try the next size smaller, or a ring with more tension.

It can take a few tries to get the technique and fit right. That is normal, and it is why complete systems come with more than one ring.

How ring sizes are measured

Ring sizes are based on the inside diameter, the width of the hole in the middle. A smaller inside diameter means a tighter ring. Some rings also come in different tensions, meaning how firmly the material resists stretching, even at the same diameter.

One important point: Pos-T-Vac and Osbon size their rings differently, and the rings are made for their own systems. A size that works in one family will not tell you which size to buy in the other. Pos-T-Vac rings load onto the cylinder with the Pos-T-Vac ring loading cone. Osbon rings load onto the ErecAid cylinder by hand or with the Easy Action Ring Loader. Reorder the ring style that matches your pump.

Pos-T-Vac ring sizes

These rings are for Pos-T-Vac systems, including the MVP 700, BOS-2000 and Automatic 3000. All are latex-free.

Ultimate Rings: soft and pliable

Ultimate Rings are soft, round rings that give even tension. The MVP 700 ships with Ultimate II rings in sizes 1, 2 and 3.

Each Ultimate Ring lasts about 20 to 30 uses. The manufacturer recommends replacing rings every 3 to 6 months, depending on how often you use them.

Mach Rings: a thicker center

Mach Rings have a thick center that spreads tension evenly over a wide area for comfort.

A Mach Ring keeps adequate firmness for about 30 to 40 uses. Replace it sooner if it stretches, tears or no longer holds tension.

Notice that the two families do not line up number for number. An Ultimate 2 and a Mach 7 share a 10.5 mm inside diameter, but the rings are built differently and may feel different. If you switch families, compare by the millimeter size, not the number.

Ring Kit

The Ring Kit includes two Ultimate II rings (size 1 at 8.7 mm and size 2 at 10.5 mm), a loading cone, an applicator, 1 oz lubricant and instructions. It is designed for men who can get an erection but have trouble keeping it, and no pump is needed. If you need a pump to create an erection, start with a complete system instead.

Osbon ErecAid ring sizes

These rings are for Osbon ErecAid systems: the Esteem Manual, Esteem Automatic and Classic. Each of those systems comes with four Osbon tension rings.

Standard and high-tension rings (A to D)

Osbon uses letters for size and tension. These rings have raised bumps on the upper side and a "U" notch on the underside.

  • Ring A: large, standard tension, 22 mm
  • Ring B: large, high tension, 22 mm
  • Ring C: medium, standard tension, 19 mm
  • Ring D: medium, high tension, 19 mm

Osbon rings can be used alone or in combination. The user guide that comes with your system shows seven combinations for different girths and results, so check it before you buy more rings.

MaxElasticity rings: the lowest tension

MaxElasticity rings have the least tension of Osbon's standard rings. They suit men who need only a small amount of tension to maintain an erection.

EZ Rings: fit on the end of the cylinder

EZ Rings fit on the end of the cylinder like a lid, so scrotal tissue is not drawn into the cylinder. Once the erection is created, the ring comes off the end of the cylinder and stays at the base. Size 4 is the tightest.

  • EZ Ring 4: 16 mm, the tightest EZ Ring
  • EZ Ring 5: 17 mm, higher tension than the Osbon standard rings
  • EZ Ring 6: 18 mm, tension similar to the "D" ring
  • EZ Ring 7: 19 mm, tension similar to the "C" ring

Comfort Ring: soft and disposable

The Comfort Ring is one size, made of soft, highly elastic material, and meant for one-time use. It suits men who find standard rings too tight or rigid and need less pressure to maintain an erection. It is sold alongside the Osbon ring range.

Osbon standard and MaxElasticity rings last about 1 to 6 months, depending on how often you use them.

When to try a different ring

The ring is uncomfortable or painful

Try a larger size, or a softer or lower-tension ring: an Ultimate Ring instead of a Mach Ring on Pos-T-Vac, or a MaxElasticity ring or the Comfort Ring on Osbon. Pain is a reason to stop and call your doctor, not to push through.

You notice small red spots or bruising

MedlinePlus says small red spots under the skin or minor bruising can mean you are using too much pressure or the band is too tight, and advises stopping use until they go away (MedlinePlus). Contact your doctor about serious bruising, blood blisters, pain, or decreased sensation.

The erection fades too quickly with the ring on

The ring may be too loose. Try the next size smaller in the same family, or the same size with more tension (on Osbon, B instead of A, or D instead of C).

Scrotal tissue gets pulled into the cylinder

Osbon users can try an EZ Ring, which seals the end of the cylinder. We also carry scrotal shields in 3/4" and 1" sizes, which sit at the open end of the cylinder to limit scrotal tissue from being drawn in. If you feel pain, stop and talk with your clinician.

Getting the ring onto the cylinder is a struggle

Use the loading tool made for your system: the ring loading cone for Pos-T-Vac, or the Easy Action Ring Loader for Osbon. The Esteem systems already include the loader, and it is sold separately for the Classic.

The ring has stretched or worn out

Rings lose elasticity with use. Replace a ring when it looks cracked, sticky, or permanently stretched, or when it no longer holds tension. If a ring that used to work starts feeling loose, it may simply need replacing rather than resizing.

Safety basics

  • Never wear a tension ring for more than 30 minutes, and never fall asleep with one in place.
  • Allow 60 minutes between uses (MedlinePlus).
  • Use a water-based lubricant. Never use petroleum jelly, which can damage the device.
  • Talk with your doctor before using any vacuum device if you have a bleeding disorder, sickle cell disease, or a condition that can cause priapism, or if you take blood thinners.

If you are using vacuum therapy after prostate cancer treatment, your urologist may have specific instructions about rings, including whether to use one at all during rehabilitation. Our patient guide explains more.

Find your ring

Browse every size in our All Tension Rings collection, or see the tension ring section of our FAQ. Every order ships in a plain, unmarked box. Not sure which size to try next? Contact us and we will help you compare.

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