When using the model 373 or 374 Solder Feeder units, the Hakko B5183 Spacers are required when attaching the tube unit (models B3477 or B3478) to the FX‐1001 Handpiece. The spacers are a foam rubber with adhesive on one side. The larger spacer should be attached to the bottom of the tube unit using the adhesive side. The smaller spacer should be attached to the larger spacer, again using the adhesive side. After the spacers have been attached, the tube unit can be attached to the handpiece using the metal clips that were included with the tube unit.