Screw-combination cock ring and ball stretcher. This wicked stainless steel device locks together with a single screw on each side, for a good tight fit. Opens
and closes with the provided allen wrench.
Remember, the ball stretcher has to be tight enough or else the stretcher would slip off. At the same time, you don’t want it to be too tight. For most men, the ball stretcher diameter should be about 75 to 80% of their ball diameter. Anything smaller than that, and it may be too tight for you to wear.
With this in mind, measure around your sack just above your balls with a tape measure or a string to get the circumference.
Then divide that by 3.14 to get the inside diameter
Then convert your inches measurement to millimetres