The sealed brake ducts work not for brake cooling benefits but for aerodynamic gains. Ferrari first introduced the “barrel” or “bucket” ducts in 2001. usually air flowing around the front wheel passes either side, the flow towards the inner face (facing the chassis) passes into the brake duct scoop and is circulated inside the brake disc and vents through the drillings in the disc, on open brake ducts this flow could then flow through either the inner or outer face of the wheel. Also the flow passing the outer face of the wheel had a tendency to pass through the openings and in the lower pressure region between the wheel and the chassis. These mis-directed flows were previously acceptable, but when the front wing height was raised (for 2001) Ferrari sought to block the flows, forcing the heated flow from the brakes through the outer face of the wheel and deterring the flow past the outside of the wheel from passing through.

Many teams followed this design in 2001, Williams were late adopting them in 2002, while McLaren have only just run them as part of the MP4-18 braking set up.
Ferrari this year tidied the path of the heated brake flow, but adding a donut shaped fairing on the outside face of the disc, this gave the flow a neater path to follow through the spokes of the wheel.
Jordan and Williams have also adopted this set up this year.