Carbon fibre filaments.
The brush bars of most vacuum cleaners only have nylon bristles. These work well on carpets but are not as effective on hard floors where fine dust can be left behind.
The DC44 brush bar has both stiff nylon bristles and anti-static carbon fibre filaments. On carpets, the nylon bristles remove ground-in dirt. And on hard floors the carbon fibre filaments remove fine dust.
Carbon fibre filaments
Ultra-fine anti-static carbon fibre filaments clean hard floors.
Stiff nylon bristles remove ground in dirt from carpets.