Psidium friedrichsthalianum, the Costa Rican guava or cas, is a species of guava found mostly in Costa Rica but also grown in Guatemala, Nicaragua and other Central American countries.

This fruit is commonly used to prepare a sour and refreshing drink.

It is used as the base for fresco de Cas, in which Costa Ricans mix it with sugar and water and sometimes add cream for a slightly acidic fruit drink.

[1] The cas fruit was described by Otto Karl Berg in 1893.

Media related to Psidium friedrichsthalianum at Wikimedia Commons