PRO Marked-Line by Rino-Tuff is a professional grade trimmer line that outperforms other lines on the market. Innovative line marking every foot allows fast and easy reloading to make respooling easier. Scientifically engineered to be more durable and last up to 50% longer than residential trimmer line. Impact modifiers are embedded within the nylon to keep your line from breaking away when trimming against obstacles as often as other products on the market. That means cutting more with fewer stops to get the job done faster.