Re: slow,medium ,fast med/fast etc etc please explain
I was referring to the action of the rod and how the line slides throught the guides. (slickness, not being abrasive) Lower quality lines also tend to coil up and not float all that well.
I doubt there are any fly lines on the market that are abrasive enough to damage the guides on a rod straight out of the box. I added that "straight out of the box" clarification because it is very possible that a line cast on asphalt, pavement, or even sand could pick up grit that could damage the guides on a rod.