Portwest - 6m Retractable Fall Arrest Block - BlackThis Fall arrest block comprises of a retractable lifeline made of wire rope which is stored on a reel, within a protective housing. The reel is spring based to wind the retractable lifeline in and incorporates an inertia brake mechanism, which allows the lifeline to be slowly extracted and automatically retracted to accommodate the users body movements. It also comprises of a swivel snap hook with a double safety lock and fall indicator. Size Range: