Cloneboy Helper Ring

The Cloneboy is a kit that allows you to make a mold of... a certain masculine body part. I hope this is okay here as this item is not explicit, nor is the name of the product it is designed for.
When using the kit, you're asked to slit the plastic tube of the packaging, re-tape it to 6 cm in diameter, and then put a rubber ring over the end... and the packaging is thin plastic and it just collapses in an irregular fashion, and clearly will not work to make a good mold.
So this is just a very very simple ring with an outer diameter of 6 cm to fit inside the tube at one end, to keep it from collapsing before you put the black rubber thing on that end. Also lets you easily size the tube to exactly 6 cm without having to measure. Works great for its intended purpose, and prints in about 5 minutes at .4 mm layer height.