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Go to WWW.ATSFNSCALEMODELS.COM for further information on this model (used in all tender trucks) and on other ATSF N scale models.
The short extensions are used to create all-wheel power pickup under the tenders.
Cut FVM wheel axles in the middle (about) using a grinding disk (wear eye protection) and insert the all metal halves into the short extensions (clean all burrs from the cuts). The extensions have a solid division in the middle to prevent electrical contact between the axle halves. It is a nice fit so try to push them not to far..... pulling back could be difficult without damaging the extension. Apply a little ACC glue into to holes to secure the halves after the wheels have been set to the correct gauge.
The insulated halves can be pushed into the long extensions to be used under freight cars........ no need to throw them away.