Mersen open style Class J fuse blocks accommodate all Class J fuses ranging from 0 to 600 A, 600 V. A choice of screw, pressure plate, box and special order stud connectors fit a wide range of stranded or solid copper or aluminum wire. Insulators are either molded glass filled polycarbonate (GFPC) or phenolic with verified dielectric strength in excess of 2500 V. SJ fuse blocks are more compact than the traditional offering and feature a unique adder block configuration for multi-pole field assembly. All fuse clips are made of high conductivity tin plated copper, with a choice of spring reinforced or non-spring reinforced clips.