330 foot fiberglass tape displays SAE on one side and metric on the other. Protruding marker at the bottom of case makes measuring easier. For long distance measuring. It's tougher, more flexible and safer than steel. Gives more accurate and longer service, as proven by numerous field tests. Won't rust or corrode. Stains disappear by water washing. Large handle speeds operation. High impact. One piece molded plastic case so smartly yet functionally designed, it won industrial design award of UNESCO: Precision measurement with your tape measure. Important: Temperature correction is not necessary in normal use with tension of 4.4 lbs or less applied to the tape measure correction to compensate for elasticity is seldom require. In general survey, however, greater tension is usually used and the following correction should be made: Measurements obtained at 1lbs. tens on should be corrected by 0.02in per 3FT. Measurements obtained at 22lb. tension should be corrected by 0.04 in per 3ft. The tape measure will return to normal after tension is removed.