PFERD Stringer bead twist knot wheel brush is tightly twisted for low flex, high impact brushing action. Designed for root and hot pass weld cleaning in pipe joining applications. Also for general use where a narrow face, aggressive brush is desired for controlled, confined surface contact area. Designed for applications requiring aggressive brushing action. Recommendation use for optimal performance, use on angle grinders. Available in POP packaging. Specification: Diameter (inches): 4-1/2; 5/8-11 Thread; Wire Size: .020; Trim Length (inches): 1; Face Width (inches): 3/16; Maximum Rotational Speed (RPM): 20000; Filament Material: Carbon Steel Wire; No. of Knots: 32.