Duff Beer is the most popular brand of beer in Springfield. It is Homer's favorite beer and is enthusiastically promoted by Duffman, the company's mascot.
The quality of Duff appears to be standard for mass quantity supply beer. Strict regulations are supposedly maintained at Quality Assurance. Such a foothold for good supply may be the only filter as portions of Duff Beer contaminated by rats, body parts and even Hitler's head have been spotted.