Of these, a record-tying seven strengthened into major hurricanes, a record-tying five became Category 4 hurricanes and a record four reached Category 5 strength, the highest categorization for hurricanes on the Saffir-Simpson Hurricane Scale. Among these Category 5 storms were hurricanes Katrina and Wilma, respectively the second costliest and the most intense (by lowest pressure) Atlantic hurricanes on record. This season was also notable because the list of storm names was used up and six Greek letter names had to be used.