The Self Lock Series of tape measures is a unique line of tape measures. The 25-foot x 1-inch inch/Engineer scale allows for engineers to take measurements with ease as the Self Lock Series features a unique self locking mechanism that allows the blade to extend smoothly as well as a push button release that insures complete control when retracting the blade. This is the ideal measuring tool for engineers in the field or for any DIY'er . The series also provides an impact resistant rubberized case and a nylon coated blade for maximum durability.