Yup, it's Sitrus.
Generation III
A Sitrus Berry, if held by a Pokémon, can restore 30 HP when its HP drops to below ⅓, or can be used as an item to restore 30 HP at any time.
Pokémon Mystery Dungeon series
A Sitrus Berry recovers all of the user's HP when used. Additionally, if eaten when the user's HP is full, the user's maximum HP is increased by 2.
Generation IV
When held by a Pokémon, a Sitrus Berry will restore ¼ of its HP when its HP drops to below ½. It can also be used as an item to restore ¼ of a Pokémon's HP at any time.
Generation V
When held by a Pokémon, a Sitrus Berry will restore ¼ of its HP when its HP is below ½. It can also be used as an item to restore ¼ of a Pokémon's HP at any time. Due to a glitch in Pokémon Black and White, dropping below half HP by taking self-inflicted damage from confusion will not activate the Sitrus Berry.
~Bulbapedia
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