The brush knots are knotted to 50% of the length. The brush achieves a better surface quality on uneven surfaces than conventional knotted brushes. Steel wire is the most common filament material. Brushes with steel wire as the filament material are ideal for work on surfaces and deburring. PFERD special wire has high tensile strength and bending fatigue strength. This ensures that the wire wears down in the optimal way, as well as a long tool life, even in extreme brushing applications. Steel wire is temperature-resistant up to 600°F.