These look great! I may have missed it, but are these scale, or traditional Lionel sized?
Tank cars in the steam and early diesel era were in the 8000, 11,000 gallon capacity, so that would translate into a scale size between around 9" to 11" I suspect.
A lot of folks don't know it, but the Lionel so-called "traditional" single dome tank cars (8000 gal.) are scale sized. They are 10 1/2" long (including couplers). (The RMT cars are listed as 10 1/2" as well; I don't know if that's with the couplers).
Smaller prototypical tank cars in earlier years could be as short as 31' long (Dow, Dupont and IMC had some of these, for example), but many of the 8000 gal. tank cars in the late steam/early diesel era were around 40' in length (or so I read). In 1/48 scale, that equates to 10 inches in length.
Some time ago out of curiousity I compared a Lionel "scale" 8000 gal. car with one of the Lionel "traditional" 8000 gal. cars. The "scale" one was wider, but not as long as the "traditional" version. Just eyeing them, they would both appear to be about equivalent as to having an 8000 gal. capacity.
Of course, tank cars, like box cars and everything else, came in all sorts of different sizes. Point is, though, it appears the RMT tank cars, as well as Lionel "traditional" tank cars, are both of sufficient size to be considered 1/48 scale. Appearance-wise, they're both pretty much dead ringers for the typical General American 8000 gal. tanks, and others as well.
