Metal free brushes are a innovative solution to cleaning the inside of pipes and tubes without scratching them. This brush line is entirely customizable to your specific needs. The standard line of metal free brushes features a soft .010 mono filament fiber fused to a poly rod. All parts are polypropylene. As of 12/2011 we are using a stiffer (.016") bristle for brushes that are 1 1/2" OD and larger.