Mersen open style class J fuse blocks accommodate all class J fuses ranging from 0-600A, 600V. 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 2500V. 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. 600 Volts 30 amps Space Saving Adder poles Box connection.