Page "The Legend of Zelda: Majora's Mask" Paragraph 9

Other masks provide situational benefits.

For example, the Great Fairy's Mask helps retrieve stray fairies scattered throughout the four temples, the Bunny Hood allows Link to run faster, and the Stone Mask renders Link invisible to most non-playable characters and enemies.

Less valuable masks are usually involved only in optional side-quests or specialized situations.

Examples include the Postman's Hat, which grants Link access to items in mailboxes, and Kafei's Mask, which initiates a long side-quest to receive the Couple's Mask.