M-320 is a type of illegal firework sold at the Li'l Valu-Mart. Homer Simpson bought one when visiting the shop. He intended to use it outside in order to celebrate Independence Day, although he was forced to abandon this plan when he learned from Bart that he not only was fresh out of matches, but didn't even have a substitute such as a lighter on him either. He then unwisely lit it with the stove in the house which the Simpson family was staying at, and tried to subdue it by stuffing it in the dishwater (he originally opted to store it in the fridge, although he changed his mind at the last second upon realizing that would risk destroying the beer supply as well). It destroyed the house's plumbing so that the sink began to overflow with sludge, which Marge ended up having to clean up afterward.
