Stack module holds two additional drums to double the entire system capacity to up to four 30- and/or 55-gallon (110- and/or 200-L) drums of Class 1B or 1C flammables and combustibles or nonhazardous liquids
When storing both 30- and 55-gallon (110- and 200-L) drums, the smaller drums should be placed on the top of the stack module