ISC RP200 Series Rigging BlocksThe ISC 200 Series Pulleys are redesigned versions of the popular ISC arborist blocks with 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 arborists put on their blocks, and the unique axle and frame interlocking design means that these pulleys are up to 150% stronger than their predecessors. The Patent Pending SafeLock system is an updated