What word in Russian is the grade of caviar?

The word for "grade" of caviar in Russian is сорт (pronounced "sort").

For example, you could say:

* "Этот сорт икры очень дорогой." (This grade of caviar is very expensive.)

* "Какой сорт икры вы предпочитаете?" (What grade of caviar do you prefer?)

Keep in mind that "сорт" can also refer to the "variety" of caviar, which is a slightly different concept.