That is standard Gilbert S gauge track. As I said above, the radius was listed as 20" by Gilbert, but that is to the outside of the ties. The centerline radius is 19". Gilbert only made that radius. K-Line made matching track in 27" radius but it is not plentiful so it will be more expensive than the original Gilbert track. K-line also made 36" straight sections. The easiest way to tell Gilbert from K-Line is Gilbert track has gray insulators, K-Line uses black.