The moving contact component of a direct sliding potentiometer that slides along a resistive body and leads out an input voltage is called a brush. That is, the brush made of metal materials; The other is a carbon brush, that is, carbon morning I drowned chu and tree fingers and other mixed materials produced by the brush. The shapes of metal brushes are brush, point, sphere and multi - finger. In order to ensure the contact reliability and current distribution uniformity, the multi-finger brush has the best effect. The shape of the carbon brush is conical and rectangular, and the contact surface is flat or spherical. The contact reliability, low noise, mechanical durability and service life of the direct sliding potentiometer are directly related to the contact state and mechanical wear of the resistance body of the brush. Therefore, brush material should have corrosion resistance, oxidation resistance, heat resistance, cold resistance; Good thermal conductivity, good electrical conductivity, no magnetic, low contact resistance, high wear resistance and good mechanical strength.