Having a proper ball gap is critical for comfortable long term wear of a chastity device. This post from Newbie Sub is a good starting point for more information on why: https://www.reddit.com/user/newbie-sub/comments/1h526fd/chastity_advice/

If you prefer an curved ball ring, you can bend the ball ring by placing it in boiling water for 2 minutes. See my reddit post for more details: https://www.reddit.com/r/chastitytraining/comments/upkh5a/adjusting_the_gap_on_plastic_cages/

Use these ball and shaft sizing rings to determine the following measurements:

1. Ball Ring Diameter: kit includes ball rings in 1mm increments.
2. Shaft Ring Diameter: kit includes shaft rings in 1mm increments.
3. Ball Gap: adjust the shaft ring to a comfortable height and use the notches on the ball ring posts to record the height. Remove device and measure ball gap.
4. Shaft Length: measure from the top of the ball ring to your the tip of your urethra.

Printing: 0.2mm layer height 4 walls 15% Infil

Installation:

1. Put on ball ring
2. Put on shaft ring
3. Use M3 x 16 mm bolt with two washers and a nut to secure the shaft ring to the ball ring
4. Adjust height of shaft ring until comfortable and balls don't slip between the rings
5. Tighten nut to compress the shaft ring tab between the ball ring posts. I use a hex key for the bolt and a pliers for the nut.