The Stens Fire Round Trimmer Line features a round shape and is highly durable when contacting concrete, landscape rocks and trees. This general-purpose trimmer line is a good choice for a variety of trimming jobs around the yard because of its versatility. To enhance its strength, the line is made from a copolymer formula that blends 2 different materials. Copolymer line is more resistant to stretch and breakage. Round trimmer line is meant for multi-use trimming applications around the yard. The round profile exerts less drag on the motor of the trimmer and wears down less quickly than other shapes of trimmer line. It also tends to be easier to load in the trimmer and breaks off less frequently. The trimmer line comes in an intense red color that stands out in the lawn, making it easy to spot pieces that break away.