16'' Polypropylene block, filled stiff blue polyester. The filaments (grey only) are metal detectable and X-ray visible. Should fibers come away from the brush and get into a production line, they will likely be detected by most correctly calibrated metal detection systems. Ask for sample fibers to conduct your own tests. The gripped handle is comfortable to use even in gloved hands. See also the 100% detectable D9RESMDX.