When lifting the drum into position a connector on the back of drum automatically hooks up to a pipe in cyclone this way creating a low pressure in bottom of the drum. This is designed to hold down plastic bag to avoid it being sucked up into the cone during use, no other cyclone or dust system has such a smart system, it is a vast improvement over last generation. Laguna MDCPF32201 P|Flux: 3 3HP Cyclone Dust Collector