The 15" curves _are_ small, but short, switcher engines (like the SW9/1200), small steamer (0-4-0. 0-6-0, and maybe a 2-6-0 and 4-4-0) and short cars (40 foot boxcars, 34' shorty 'beer can' tankers, etc) will work on it. in 4.5 ft, if you expand your turn space, you can use the 22" curves...