This is a four pack of blister carded curve track pieces for use with the UNITRACK N gauge track system. The Curve radius and degree descriptions describe what portion of a complete circle (360º) is made from each section and how big that circle will be (in this case approximately 12", or double the radius). Radius measurements for curves such as these are measured from the center point of a circle to the center line of the track, making it easy to keep track of how large your layout will be when you're still in the planning stages! Please note that UNITRACK Compact is designed for locomotives and cars that can navigate very tight radius curves, such as light rail vehicles and other small locomotives and as such they may not be compatible with all N gauge trains.