The Atlas left hand remote snap switch track has a remote control switch machine attached so you can wire the switch to be "thrown" (changing the direction of the rail), from your control panel, rather than from the switch itself. Comes with a 1/3 18" radius section, making the curved leg equal to an 18" radius section. To add a passing track and siding, simply replace with a 9" straight section. When replacing an 18" radius curved section with an Atals Snap Switch, add a 1-1/2" straight section to the opposite side.