Mounting slots (516 x 12) one at each end standard on stock heaters Stock heaters are rated at 40 watts per square inch and 60 watts per square inch; 120 and 240 volts, Screw terminals 10-32 double nut stainless steel, Nickel-chromium (8020) resistance wire coiled on custom machines assuring accurate rating, Ceramic insulation MgO (magnesium oxide) high purity with excellent heat transfer capability when compacted.