Standard Rings: 8mm thick. These work for most people.
XD Rings: Extend forward by an extra 2.5mm. This tightens the gap, and also makes the rings more rigid. Good for people with smaller balls to prevent escape.
Curved Rings: 5mm backward curve at the bottom. Good for troubleshooting pressure under the scrotum. Please note that people with smaller balls can be more likely to slip through the gap.
| Size | inches | mm |
|---|---|---|
| 0 | 1 1/2 | 38.1 |
| 1 | 1 5/8 | 41.3 |
| 2 | 1 3/4 | 44.5 |
| 3 | 1 7/8 | 47.6 |
| 4 | 2 | 50.8 |
| 5 | 2 1/8 | 54 |
| 6 | 2 1/4 | 57.2 |
| 7 | 2 3/8 | 60.3 |