tippet

You don't HAVE to, but the section of a tapered leader that is the X-rating listed on the package is only about 18 inches long, so as a day goes you use up that 18 inches and then need to attach tippet or have a heavier leader. Or, say you're fishing with 3x (good for size 8, 6, 4) flies, but decide to use a size 18 fly. You then need to bring that 3x down to a size more fitting to a size 18 fly, like 5x. Maybe you buy mono leaders and then attach flouro tippet as a way to save money. Start with a 9 foot leader of the X-rating you expect to need based on the flies you want to use and the fish, and go from there.

psu_fish: When I started fly fishing I had a hard time making the correlation between fly size and tippet size. An old head taught me that a real simple way to know what size leader/tippet to use is to take your fly size, divide it by 3, and use that size of tippet. Size 12 dry fly- 4x tippet. Size 10 streamer- 3x. Size 18 dry fly-6x. Now, theres leeway to that too. a Size 6 is fine on 3x, a size 20 is ok on 6x, but the divide by three method is a good way to get your bearings at first.

I never took the divide by 3 rule very seriously except for fishing dries. I suppose as a VERY general guide for sub surface fishing it may have some merit.

When I am fishing streamers I am generally targeting bigger fish and visibility of the tippet means nothing in that case. I won't touch anything smaller than 2x for #10-12 streamers, and for anything larger than that I will use 1x or heavier. It takes a good bit of force to bury a #4 hook. I have learned the hard way why it is a bad idea to go too light when fishing big streamers.

When I am nymphing for steel, I mainly use 4x but if conditions permit I will use 3x. This is for all flies from #8-18. I let water conditions and fish size dictate the tippet I use for the most part.