Are you talking about the flexible line that connects the caliper ro the hard line? If so then YEA, many, many of us use them. They are worth upgrading IMO, they give a slightly (barely noticable) stiffer pedal feel, but more importantly they are a lot more tough than the OE flexible lines that come on our jeeps. And they last longer.
For shopping, I would call up David @ Northridge, tell him what you have and what you want and he will hook you up.
I'm running the Crown stainless lines and have for a few years now. The outter uv coating has cracked and peeled off in a few areas but they're holding/working great. Many other lines don't have that outter uv coating at all so I'm not sure if it's just a gimmic or what but I see a lot of lines just plain braided stainless so I don't think there's any issues to run it like this. My thought was the coating would help keep sand/mud/debris out but I honestly don't think it makes any difference. I can't say I noticed any change in braking or how they felt after the swap, but they say you won't get the expansion from the stainless as you sometimes do with worn out factory lines. I think they're worth it if you need them. Not too much more than factory lines anyway.
The Crowns you have you get to pick the color you want.
With the factory lines you can end up with breakages as rubber ages.....I had it happen to me on a 1983 old truck ( Range Rover). Happened after a steep climb somehow the rear hose was old and pinched itself on the connector. I upgraded to stainless right after this.
I use the SS steel types from Classic Tube, http://www.classictube.com/ They will make any length you want, so it doesn't matter what lift and how far you flex, just need to give them a measurement.
I had them develop a SS flex line for the Liberty, and in all my research, I found out in the environment we play in, it is imperative that we use a line that is coated or shielded, do not use a bare SS flex line on your DD. Over time the mud and fine particles get lodged in the braiding, grinding away until the line fails.
Crown brake lines have the Kevlar coating on them!
Don't know if they always have had the Kevlar coating?
But they look pretty cool in the colors they offer! Plus there customer service is great!
Talk to the rep at Offroad Expo and he says, if you order from Quadratec, make sure there
The crown versions! He said Quadratec mixed up another brand with there's!
So now there shipping two different types of Brake lines!
You have to make sure the lines do not contact anything, they are not very durable to rubs and if the stainless rubs through they will blow out. The stock lines are more tolerant because the rubber outer is not what keeps the pressure in. I have lost 2 stainless lines over the years because they moved on the trail and rubbed through is short time.