These trucks are intended for use with N Scale Kits FD2 Heavy Duty Depressed Center car kit available from http://www.nscalekits.com
The package has four trucks for use with the kit. The truck is designed for use with MicroTrains and Fox Valley Models wheels. The trucks are also appropriate for N Scale Pennsy T1 steam locomotive tenders too. These trucks are a revised version.
The trucks are also used for the FW1 car, available from the Keystone Detaiils shop on Shapeways http://shpws.me/LiuT You will also need the car ends available from http://www.nscalekits.com