https://www.unileverfoodsolutions.us/product/hellmann-s-extra-heavy-mayonnaise-4-gal-1-pack-1-EN-639543.html

https://www.webstaurantstore.com/hellmanns-real-mayonnaise-24-gallon-drum/125HLMN8828.html

https://www.unileverfoodsolutions.us/product/hellmann-s-extra-heavy-mayonnaise-tote-2300-pound-pack-of-1-1-EN-1210411.html

The largest sold to consumers through normal channels is a gallon. Typically used by people who are feeding a lot of people, like making a dish for a large family gathering, or by people who only go shopping once a month or less. Some people live an hour from the store, so they just buy an excessive amount of food and shop infrequently.