Connect Core Running Line is quickly becoming a favorite of switch and Spey casters. If you like a coated (non-mono) running line then check this one out.
It has almost no stretch to it so you can feel even the tiniest of grabs. Compare that to a stardard core running line with 30% stretch. The majority of the running line is thin diameter for easy shooting and then right before the head attachment the diameter thickens up for easy handling. The line has a color change every 10 feet so gauging the distance of your cast is easy.