Actually LGB makes 3 different curved switches
R1 4 foot diameter.
R3 8 foot diameter.
R5 12 foot diameter.
Also, trainli specifies that their R # is true radius, be sure to download their track manual for the metric /US measurements. It is LGB that created numbers not relative to the radius and was a psuedo standard. Be careful with US measurements as the switches (curved track) are really metric measurements and rounded off to nearest US measurements.