Hopper cars for the transportation of bulk cargoes. For protection from the weather,
applied covered hoppers with loading hatches on the roof.
The model is presented in SMNX)

I recommend to use IMGTools. open gta3.img (is in a folder models in the catalogue with game).
Use command "FIND" to find and delete files freiflat.dff è freiflat.txd,
and command "ADD" insert files from archive.

You can also set the car instead of the standard covered wagon "freibox".
Rename the file freiflat.dff and freiflat.txd to freibox.dff and freibox.txd.

Default wagon "freibox" does not appear in the railway traffic. For appearance in game,
you should use SA Train Limiter utility to assign it to one of the trains.