R40 curves have a radius of 40 studs, measured from the centerline of the track. The outside diameter of a circle of R40 curves is approximately 14″ (352mm). A single track segment covers 22.5°.

These official tracks from LEGO® 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 1/2 circle.