Berkley Trilene 100% Fluorocarbon ice Fishing - A specially designed 100% fluorocarbon formula for ice fishing. Thinner diameter and more supple to stay flexible in cold weather conditions. Low stretch formula for greater sensitivity and solid hooksets Thinner diameter for better lure control Ultimate Invisibility - The invisible fluorocarbon. Similar refractive index as water so fish can't see it Excellent Manageability - Lower memory for superior handling