i use a barrel swivel to attach tip-up line to my leader. If you are looking for the best kind of line for a leader you will have to be more specific what are you fishing for? when setting them up for perch, walleyes, or trout (basically anything but pike) I like 6 lb mono . If you have pike around but aren't targeting I would go heavier maybe 12# fluoro if it's pike I'm after I use 20# spider line. When I set my tip-ups up for most trips it is 6 lb stren that comes in the red box . anywhere between 4-8' long depending on depth usually, for me anyways, about 6' if Im not after pike and 3' or so if I am after pike. hope this helps