Mersen class R fuseholders accommodate all class R power fuses. A choice of screw, pressure plate, and box connectors 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. 30, 60, 100 and 200A fuseholders feature a unique adder block to form multi-pole segmented blocks of as many poles as desired. All fuse clips are made of high conductivity tin-plated copper 250 Volts 30 amps 3 poles Screw connection.