R120 curves have a radius of 120 studs, measured from the centerline of the track. The outside diameter of a circle of R120 curves is 78″ (1984mm). A single track segment covers 11.25°.
These tracks are all plastic, and work with any push- or battery-powered LEGO® train (namely Power Functions). They are not compatible with the older 9V or 12V train motors.
Each set includes 8 track segments, enough for a 1/4 circle.