Two-way mirror

A communication mirror is a two-way mirror that allows people to communicate with each other between locations.

During their years in school, James Potter and Sirius Black used a pair of communication mirrors so they could talk to each other while they were in separate detentions. Sirius later gave James' mirror to Harry in 1996. After Sirius' death, his mirror came into the possession of Mundungus Fletcher, who in turn sold it to Aberforth Dumbledore.

Aberforth's possession of one of the two-way mirror became a great help to Harry Potter and his companions, who were kidnapped by the Snatchers and brought them at the Malfoy Manor in the summer of 1998. During capture, Harry brought the mirror he possessed from his pouch and incidentally that Aberforth was looking at the other one so he was able to see what happening at the Malfoy Manor. Later, he sent Dobby to rescue them.