There have not been any dedicated leader materials for carp fishing which we felt left a gaping hole in a carp angler's armoury. Amnesia had been popular but it was thick for its breaking strain, which lead to large leader knots that rattled through the rings. It was soft though and knotted well but it had very little abrasion resistance.
Its performance came from its Diameter rather than the qualities of the material itself. I, like most people, had used Amnesia but felt a low cost dedicated leader with the great casting qualities, good knotting and high abrasion resistance would be a big benefit to my own fishing. This was the motivation behind the XT leader material.
The only people to work with when it comes to such a material are the American giants Berkeley. I had used their lines and braids for many years and always found them to have all the qualities mentioned above, but still there was not one single line sold on the right sized spools to make it affordable or easy to store. We persuaded them to spool a highly supple yet abrasive resistant line perfect for leaders. We requested a low vis green and that's what we got!
We felt that a 20lb and 30lb version would best suit today's carp angler. Many people use far too heavy a leader. In reality only the very best casters can break 30lb mono on the cast. If your line snaps on the cast and the lead sails out straight into the lake you have not broken the leader! It has wrapped around the butt ring and snapped itself. A true break from the force of the cast happens before the rod is fully loaded so the cast can go up in the air, off to the side, basically anywhere but straight out.
If you have small Baitrunner type reels with 8-12lb line then the 20lb will be for you and if you have heavier lines on big pit reels and 3lb or above test curve rods then the 30lb is better.
I use a 2 rod length long leader on my marker rod so the marker float doesn't tangle on the cast, which can happen with braid straight through. For your information I use 20lb Berkeley whiplash on my spod and marker rod, it is the same thickness as 4lb mono and cast like a dream, just make sure you keep it wet at all times by constantly splashing the spool with water.
Make sure you have at least 3 turns on the reel when the lead is hanging ready for a cast, 10 turns is about the maximum although top anglers have used the full 90m of the 20lb straight on the reel for close range snag fishing with very good effect.
Always straighten the leader to begin with by laying it out on the grass and pulling tightly through your fingers or a towel - curly leaders cause wrap rounds! If the leader has been on the reel for a while repeat the straightening process. Also, clean your line by winding it through a wet towel at the end of the session and it will keep the visibility low, dirty line is easier to see!