Roller for striped beads.
The recesses on the side measure the volume of polymer clay needed for each bead.

My collection of rollers:

• Sphere roller 6 8 10 12 mm - https://www.thingiverse.com/thing:7263341
• Sphere roller 5 7 9 11 mm - https://www.thingiverse.com/thing:7284435
• Sphere roller (imperial units) - https://www.thingiverse.com/thing:7272582
• Conical beads roller - https://www.thingiverse.com/thing:7293209
• Eggs roller - https://www.thingiverse.com/thing:7305589
• Ovals roller - https://www.thingiverse.com/thing:7310814
• Striped beads roller - this thing