In the Perseus myth, what reflective object did Perseus use to avoid looking directly at Medusa?

Perseus used a polished shield as a reflective surface to avoid looking directly at Medusa.

Medusa’s gaze was believed to turn living observers to stone. Athena helped Perseus by giving him a shield polished so brightly that he could see Medusa’s reflection without meeting her eyes. Using the reflection as a guide, he approached the sleeping Gorgon and severed her head.

The shield is often described as bronze or simply as a highly polished shield, depending on the version being summarized. Its important feature is not magical reflection but the practical way it allowed Perseus to orient himself safely.

This detail is sometimes confused with other gifts in the quest. Hermes supplied equipment including winged sandals and, in some accounts, a sword; the reflective shield is particularly associated with Athena and the killing of Medusa.