Which mythological artifact was specifically designed with a built-in 'product constraint' that limited who could use it?

Product design isn't just a modern concept - it's been part of storytelling since ancient times! Mythological artifacts like Thor's hammer, Excalibur, and Pandora's Box were some of history's most famous 'products' - each designed with specific features, limitations, and magical use cases. This trivia tests your knowledge about how these legendary items were 'designed' and marketed within their mythological contexts. Can you identify the clever product design principles behind these legendary artifacts?

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

Thor's hammer Mjölnir, designed with a handle too short for optimal use but with a weight constraint allowing only the worthy to lift it
The Golden Fleece, designed to be visually appealing but requiring no special qualifications for its use
Hermes' winged sandals, which could be worn by any god or mortal without restriction
The Aegis shield, which gained power from its visual design rather than having user restrictions