All Malish showerfeed brushes feature our water and chemical-resistant Tuff-Block Showerfeed System for improved performance and long lasting life. For cleaning hard surfaces, nylon and polypropylene brushes feature 0.028" diameter fill material throughout the block. Nylon is more flexible and will last the longest while polypropylene is an economical alternative. Steel wire, 0.014" diameter, is the most aggressive of the series for use on unfinished concrete surfaces.