The Vittles Vault line of stackable containers are very popular for bulk grain storage.
They are food grade and airtight. They have a large easy access opening and the ability to stack makes them space efficient. Heavy Duty construction and easy spin off and on lid. Lid features lock-down double gaskets. The body includes molded handles for easy carrying. Made from FDA approved Food Grade Plastic and BPA Free.
This one is rated for 50 lbs. The 50 lb rating means it should hold a sack of grain.
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Vittles Vault 50-Pound Stackable – multiple size options available