I see that Intermountain has wheel sets that have ball bearings. Can they be used in any truck, or are they for some special truck only?
The sets I have are the normal pointy ends, and are used under brass cabooses that roll poorly. The IM wheelsets come in just the one axle width.
IIRC, these come in 33" and 36" wheels and were designed for heavy brass cars that did not roll well. They are not cheap, at 6 axles for $20!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
I used the similar Precision Scale ball-bearing wheelsets in my LaBelle interurban kit. The brass trucks didn't have good openings for regular pointed axles, and the BB wheels really helped it to run more freely. They have no advantage in good trucks, but poor and heavy rollers do benefit.
_________________________________________________________________