Psidium friedrichsthalianum

Psidium friedrichsthalianum, the Costa Rican guava or cas, is a species of guava origin in Costa Rica but also grown in Guatemala, Nicaragua and other Central American countries. It can be found in Costa Rica as "fresco de cas”. 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.
The cas fruit was described by Otto Karl Berg in 1893.