Stringliner mason/construction line is made of durable #18 nylon with a tensile strength of 165 lbs. This contractor pack features 6 rolls of 500 ft. fluorescent pink replacement twine on 1" diameter cores. The line is braided so it is more durable and resistant to abrasion. It also won't spin as much when used with a plumb bob. The bright fluorescent pink color is highly visible.