The Dyson DC07 Valve Pipe Assembly - Steel (904246-16) is designed to transport air and debris from the nozzle, through your vacuum and into the dust bin and cyclone chamber. If you are looking at it from the front, it is located at the base of your vacuum, just above the rear wheel. To remove and replace the valve, simply squeeze the release catches.
This genuine Dyson replacement part fits the following vacuums: DC07, DC14 and DC33.