Chalk line has two times the tensile strength of traditional lines and lasts twice as long, Convenient locking button holds string in place, Holds up to a 4 oz. bottle of Stanley® Chalk, Patented chalk view case to see amount of chalk inside the case, Rewinds 3.5 times faster than the base Stanley model, Crank clutch so crank handle will not spin when pulling out string, Patented stainless-steel interlocking hook for joining lines, On-board hook storage