The G60's were from a series of hastily produced freight cars which were used as demostrator models to complement Bachmann China QJ's steam locomotives. The first production in year 2000 included a single version in red or black and can be identified by the boxes which had a sticky label in the corner which extends over the perspex window and unique road numbers that were only released with this version. These are really quite rare as they were only available to dealers, however many were later sold under the table after the QJ's sold out. Essentially they are Bachmann Industries silver series freight cars (which make US prototype models), which was a 'marginal step above the low end of the model market. Despite them being US cars, they initially sold very well due to a total market shortage of true Chinese cars. They are still readily available through most Chinese retailers, although the black versions are getting quite scarce.
These cars are pretty much at the very basic level of model railways. The main problem is that they really don't resemble a G60 tank car at all, with a barrel far too narrow, full langth walkways, the list is pretty much endless. The paint work and lettering are extremely sharp. The tooling for them has been around a long time and the physical details are not really all that impressive with chunky ladders and footsteps, and apart from the two metal handrails that run around the car, the rest of the details such as grab irons, are simply molded onto the main body shell. The rivets are oversized (and there's lots of them) and the running boards look pretty unconvincing for see through metal grates, being nearly a scale foot thick! True, they are pretty cheap, and deservedly so. At the time they filled the gap for tank cars, but they've become pretty obsolete due to the arrival of the new Bachmann China GQ70 tank cars.
They have nice rolling chemically darkened metal wheels with low profiles that should be able to run on code 55 track. They are fairly heavy, but not overly so.
Bachmann EZ mates can be replaced with Kadee #5 (standard), #58 (standard, scale head) or #158 (standard, scale head, whisker).
These are a cost effective way of populating your Chinese layout with tank cars.