Mike asks:
My question is is there a difference in brands of leaders and
tippet i have been using SA but it seems to curl on me i use 5x with 12 14
&
16 flies so didn't think fly size was the problem.

definitely a difference as you go through various brands. At the extremes,
Maxima and Mason have very stiff nylon, and DaiRiki and some of the other
Japanese brands are relatively soft. Usually, I make up dry fly leaders with
stiffer stuff in the butt section and limper,softer stuff for the tippet and
section right behind it.
The curling issue may be fly size in the case of bulkier size 12 and 14 on a
5x, due to wind resistance when you cast them. BTW, you do want a few soft
curves in your tippet when it lands, it delays slack a bit, but tight kinky
curls usually mean too fine a tippet pushing out too bulky a bug. Try a longer
4x tippet with the same brand and see if the problem goes away...
Tom