Description: ISC's attention to manufacturing details is superb. Smooth edges, bright visible colors, and smooth operations. ISC blocks are tried and true. Apart from the aesthetically pleasing curves, the ISC impact pulley is designed to work (together with textiles) to absorb the huge forces which are created by the harsh dynamics of heavy Arborist work. The side plates are produced using the best quality hot forged Aluminium and the special manufacturing process allows these pulleys to offer a highly impressive strength to weight ratio.