CREATE TABLE table_6440 ("Location" CLOB, "Culture" CLOB, "# found" CLOB, "Ball diameter" CLOB, "Period" CLOB)

What's the Ball Diameter with the Culture of Olmec?
SELECT "Ball diameter" FROM table_6440 WHERE "Culture" = 'olmec'
SELECT "Ball diameter" FROM "table_6440" WHERE "Culture" = 'olmec'