Length

When selecting a cage, you want to know your length, flaccid, along the top from the base to the tip - each cage will have this listed as the "total length", and this dimension takes into account the measurement including a standard single ring. For example, the short is 51mm, the small is 61mm. General advice is to select a cage that is 8-12mm shorter than your overall length, but some wearers can go much shorter.

The Image to the right shows a cage with a total length of 60.8mm

Diameter

Next, you want to know your diameter, or girth - Measure both the width across the shaft behind the head (eyeball it, but keep the ruler flat), then measure the circumference. Most cages typically have a 35mm diameter, and ~110mm circumference. For example, the Short and Small cages come in two sizes, 35mm diameter, and a wider cage that is 45mmx35mm for girthier shafts.

Picking a cage, even knowing these measurements can sometimes still be a challenge if you are in between sizes - some people like to have it tight on them, and others would prefer it be a little longer. I will say, don't try to go for a cage that is 35mm in diameter unless you're under 35mm - it's better to have a little room around your shaft than not.

Ring

Picking a ring is pretty tough as it's hard to measure, because you can't measure everything as it sits, you have to measure it very taught.

Please read the Gritty Woman's guide for the base ring here: (unfortunately, the site seems to no longer exist)

https://thegrittywoman.com/beginners-guide-to-chastity/part-1-fitting-and-measuring

The following is an excerpt from the above site

Measuring for the Main Ring:

The most important measurement to get as accurate as possible is the size of the main ring. (The ring that circles your testicles and penis) An incorrect fit here can cause a whole host of problems later. If this ring is too large, the cage will slip down, or fall off entirely. If the ring is too small, you will suffer discomfort and pain, fluid retention and cutting off the blood supply to your genitals. The best fit is one that feels snug enough to avoid slipping, but loose enough that blood can flow and you feel comfortable.

There is a huge difference between having “blue balls” (The slang term to describe an ache in your testicles due to being denied orgasm) and actually having blue testicles. If your testicles are turning red, purple or blue, the main ring is too tight for you and you should remove it immediately and try the next size up.

It is very difficult to get an accurate measurement for the main ring, using a tape measure. Some people recommend tying some string around your genitals and measuring that, but even this is not ideal. The best method I have discovered for getting an accurate measurement is to pay a visit to a sex shop, or a hardware store and purchase a selection of rings, starting from roughly 2 inches in diameter and reducing in size by ¼ of an inch. Make sure the rings are made from a solid material (metal or plastic) as stretchy materials will give you an inaccurate result. You also want to make sure you choose smooth, rounded rings that will cause no irritation during wear. Starting with the largest, work your way down the sizes until you find one that fits snugly, but causes no pain, redness or swelling to your genitals. When you have whittled your way down to a few rings, wear each one for a few days solid (including at night), to get a better idea how that ring feels in every condition. Some mass produced devices, like the CB6000, come with multiple main rings of varying sizes, these may help lots of men find a good fit, but is not guaranteed (you could be between sizes).

If the aforementioned method is not possible, You can try the following option, but it is almost certain to give measurements that are larger than needed. Take something like a thin USB cable (odd, but most people have them!) and wrap it under the scrotum and around the top of the shaft and pulled tight, but not cut-off-your-circulation tight. Your testicles should dangle lower than the bottom of the cord. Mark the cord in the two spots it overlaps and then unwrap it. Measure the distance between the two marks, and check out the following

Circular rough guide:

XS: 110-115

S: 116-124

M: 125-135

L: 136-147

XL: 148-160

Cherry Keeper also offers a Wide oval ring, which works out to about the same dimensions, but the XL ring would top out around 156mm or so.

Ball Gap

One of the dimensions useful for finding your fit is the Ball Gap. In Cherry Keeper, this is the direct measurement from the bottom of the cage ring to the base ring. This measurement is affected by both the size and shape of the ring, as well as the cage size, shape and it’s measurements. It’s a LOT of math, and even then it doesn’t always show the exact picture. I’ve included as much information about this as I can and it’s available for every cage and ring combination in the shop via the Cage Finder, but every wearer is going to fit differently.

The Image to the right shows a cage with a ball gap of 18.46mm

Ring Angle

In most chastity cages, the only dimensions that affect the amount of space between the cage and the ring for the testicles to rest is the diameter of the ring and the ring to cage gap (measured at the lock body). Cherry Keeper rings come with an additional degree of adjustability to help you fine tune your fit, and that’s the angle. The angle numbers tell you how much the ring is rotated towards (negative angle) or away (positive angle) from the cage relative to the "stock" ring of that style (flat or ergo). this changes the size of the gap the testicles have, and can relax or tighten the amount of space available. You can compare rings of differing angles and styles by reading the chart posted on the ring page that lists the gap to a given diameter of cage. I generally recommend starting with a non-angled ring and then tweaking from there once you find how it fits for you.

HeadLock

Choosing a HeadLock option - The idea of HeadLock that it's a smaller opening to the cage that the head has to squeeze through to get in, and the glans gets locked on the other side just by the ridge and a little bit of friction. The entire head has to fit into the depth of the cage for this to work, so look at the "depth" measurement, and compare it to the length of your head along the top. The size headlock you choose will depend on your shaft dimensions, how tight you want it to be, and the size difference between the glans and the shaft. The ring needs to be smaller than the glans and ideally about the size of the shaft, or just a touch smaller.