To properly mount the HRHA series resistors, two M4 BTR or TORX screws should be used, with the screw head applying pressure on an M4 split washer over an M4 flat washer, as shown in the “Screw Stack” picture here. Upon proper tightening, the split washer shall be squished between the screw head and the flat washer. The split washer should never be applied directly on the ceramic as it can result in cracks on the ceramic core. A flat washer between the split washer and the resistor’s ceramic housing is always recommended. Used split washers should never be re-used after the first assembly. If disassembling and re-installing the resistor, new split washers should always be used. Tightening should be performed in 4 steps as shown on the picture here labeled “Tightening order”: (1) Hand tighten the first screw until the screw head touches the split washer, (2) Hand tighten the second screw until the screw head touches the split washer, (3) Carefully apply 1.5 ± 0.2 Newton-meters of tightening force on the first screw, and (4) Carefully apply 1.5 ± 0.2 Newton-meters of tightening force on the second screw.