Rino-Tuff Trimmer Line - Tough from Cover to Core! Engineered for commercial use, Rino-Tuff trimmer line employs new technology to create ultimate cutting performance. The soft, flexible core allows for quick impact recovery, while the hard, tough sheath provides protection against abrasions and wear and tear. The superior of toughness of Rino-Tuff makes it the ideal line for trimming against concrete, trees and fences. One pound donuts of Rino-Tuff trimmer line are available in round or square shape with diameters from .080 to .155.