The ISC 200 Series Pulleys are redesigned versions of the popular ISC ARB blocks w a new SafeLock mechanism and improved strength. Using state-of-the-art stress analysis programs, the hot-forged aluminum frames are optimized for the forces ARBs put on their blocks, and the unique axle and frame interlocking design using heat-treated hardened steel axles means that these pulleys are up to 150% stronger than their predecessors. The Patent Pending SafeLock system is an updated version of the ISC SpringLock design that provides an extremely low profile along w the same quick opening action. Anodized finish. Weighs 1.3 lbs. MBS: 22,481 lbs. (100kN). Maximum rope diameter: 9/16 in. (14mm). Standards Met: CE Machinery Directive 2006/42/EC, UKCA Supply of Machinery (Safety) Regulations 2008.