N Scale Nickel Silver Plated Brass Insulated Wheelsets
These wheels follow NMRA RP-25 Standards.
One wheel is insulated from the all-metal axle.
The entire wheelset is non-magnetic.
33" wheels are used on 50 & 70 ton capacity cars (CAPY approximately 150,000 LBS or less).
36" wheels are used on 100 ton capacity cars (CAPY approximately 200,000 LBS), and on all passenger cars no matter the era.
38" wheels are used on 150 ton capacity cars, primarily the center connection trucks on modern intermodal cars with 33" wheels at the coupler ends.
Cabooses can use either 33" or 36" wheels depending on the prototype.

There is no prototype for the 34.5" wheels used for Micro-Trains trucks. These wheels should be used regardless of car type or CAPY if Micro-Trains trucks are used on the car.

The CAPY information is typically printed on model freight cars and can be used as a guide. Some cars have the wheel size printed on the sides or ends of the car in the data. If you are ever unsure of which size to use, you can simply replace the wheels currently on the car with the same size.

Wheel diameter can be measured with a caliper:
33" wheels measure (33/160=.206") in N scale.
36" wheels measure (36/160=.225") in N scale.
(160 = N scale to prototype ratio. N scale is 160 times smaller than the prototype).