Sizing Guidelines

Measure Twice, Order Once


To ensure a precise and comfortable fit, it is important to take accurate measurements. Please follow these guidelines

If you would prefer an easier way to measure, we offer a set of sizing rings.  If you have your own 3d printer, the sizing rings are also available as an STL https://www.printables.com/model/1225015-sizing-rings

Measure carefully using a flexible measuring tape, calipers, or a piece of string for the most precise results.  There are 3 basic measurements that are needed. 

Shaft Diameter

Glans Lock Diameter

Shaft Length (Optional)

A few helpful tips before you begin

✔ Take multiple measurements at different times of the day to account for natural fluctuations.

✔ Measure in a warm environment to avoid shrinkage from cold temperatures.

✔ Do not pull or stretch the penis while measuring—keep it in its natural resting state.

✔ Ensure a snug but not tight fit when wrapping the measuring tape or string around the shaft.

Measuring the Shaft Diameter

This measurement ensures the shaft cage fits securely around your shaft without being too tight or too loose.  You want the shaft cage to be somewhat fitted.  It should not be so tight that you need any lubrication to put it on. If you are an extreme grower you may find sizing up one size beneficial.  It may also  be beneficial to measure both flaccid and erect.  The shaft size should fall where between your flaccid size and erect size. 

The sizing rings are especially helpful with this measurement.  You can try various size both in both flaccid and erect states.  In an erect state, it should be tight and slightly compress the shaft, but shouldn’t cause pain.

Method 1: Using a Measuring Tape

  1. Ensure your penis is fully flaccid.
  2. Wrap a flexible measuring tape around the middle of the shaft to get the circumference. 
  3. Record the circumference in millimeters (mm) or inches.
  4. Calculate the diameter by dividing the circumference by π (3.14).
  5. Round to the nearest whole number
  6. Example: If your circumference is 100mm, your diameter is 100 ÷ 3.14 = 31.8mm. Rounded up to 32mm

Method 2: Using a String (Alternative Method)

  1. Ensure your penis is fully flaccid.
  2. Take a piece of non-stretchable string or thin strip of paper.
  3. Wrap it around the middle of the shaft where the measurement is needed.
  4. Mark the point where the string overlaps itself.
  5. Lay the string flat and use a ruler to measure the length from the start to the marked point.  This is the circumference
  6. Calculate the diameter by dividing the circumference by π (3.14).
  7. Round to the nearest whole number

Example: If your circumference is 100mm, your diameter is 100 ÷ 3.14 = 31.8mm. Rounded up to 32mm

Measuring the GLANS GRIP Diameter

This measurement ensures the glans grip ring holds securely without being too tight or too loose. There are limits to how big the glans ring can be in comparison to the shaft. The Glans Grip needs to be less than 82% of the shaft diameter

 Shaft Diameter 
 Max Glans Ring
30 
 24
32 26
34 28
36 29
38 31
40 33


Method 1: Using a Measuring Tape

  1. Locate the area directly behind the glans (where the shaft meets the head).
  2. Wrap the measuring tape around this area or use calipers to measure across.
  3. Record the circumference and divide by π (3.14) to find the diameter.
  4. Round up to the nearest whole number

    Example: If the circumference is 90mm, the diameter is 90 ÷ 3.14 = 28.6mm. Rounded up to 29mm

Method 2: Using a String (Alternative Method)

  1. Wrap a piece of string around the area immediately behind the glans.
  2. Mark where the string overlaps.
  3. Measure the length of the string with a ruler.
  4. Record the circumference and divide by π (3.14) to find the diameter.
  5. Round up to the nearest whole number

Example: If the circumference is 90mm, the diameter is 90 ÷ 3.14 = 28.6mm. Rounded up to 29mm

Measuring the Shaft Length (Excluding the Glans)

This measurement determines the appropriate shaft cage length, which should not exceed 60% of the total shaft length It is not recommended to cover the entire shaft. Too short is better than too long.  Too long of a shaft cage will cause undue pressure on the glans and could cause irritation.  If you do not provide a custom length, the default length of 22 will be used. This provides the minimum length necessary to  remove access from the glans ring.

The measurement should be rounded to the nearest multiple of 2mm, between 20mm and 34mm.  The final shaft cage will be roughly twice as long along the bottom.  For example a 22mm shaft length will end up with a cage that is 22mm along the top and 40mm along the bottom.   

  1. Ensure your penis is fully flaccid.
  2. Place a ruler or measuring tape along the top of the shaft, starting at the base (where the shaft meets the body).
  3. Measure only the shaft length, stopping where the shaft meets the glans (do not include the glans itself).
  4. Multiply the measurement by 0.60 (60%) to determine the appropriate shaft cage length.
  5. Round this number to the nearest multiple of 2 between 20 and 34.

Example Calculations:

If your shaft length is 52mm, 60% of that is 31.2mm, which rounds down to 30mm.

If your shaft length is 40mm, 60% of that is 24mm.

For any questions regarding measurements or fit, please contact our support team at support@hzd.us