OK, sounds silly maybe, does it have to be 100% poly or is it just the 20% I’v been finding? I like to use the stuff that the pattern calls for, in this case, the wing on a klinkhamer, I use deer hair right now and thought I’d try an easier way for the wing post, like on wooly boogers, now I have reel red wool yarn for the tail , where as b-4 i used substitutes, the real wool yarn was harder to find.
Grubb,
On flies intended to float, like the klinkhamer, a wing material that doesn’t absorb water is desirable. I tend to favor Antron or Z-lon for wing posts, but that’s a personal choice and not a hard fast rule. I’ve gotten most of my Antron from Hook and Hackle and it’s pretty cheap as materials go. If memory serves me correctly less than $2.00 for a very generous card full.
Antron, Z-lon, Hi-Vis, Phenex Craft Yarn (cheapest), Polypropylene yarn (macrame) …all works fine. Hi-Vis is my favorite.
My two poly yarn favorites are Widow’s Web, which fluffs up beautifully when combed out, and Niche’s “Siliconized poly-yarn”, which is a little straighter and seems to be finer.
Joe
A source of Phentex poly yarn I have used is Yarn and Stitchery Alcove. Reasonable shipping rates for a single skein of the stuff and a decent selection of colors. I also use it to tie strike indicators.
Regards,
Steve (dragonrider)
Why cut your chances of success to 20%? 
That would be like catching the fish of a lifetime, and some bigger fish eats all but the head before you land it, leaving you only 20%. 
I seriously dought you only put 20% of your real talent into tying. I bet you have a passion about it and that’s why you sit down to tye.
So for the sake of your efforts, why not find what you really want and not compromise? 
Thank you all for your replies, I will look today more intently for 100% poly…
I’ve been using this poly that works great for strike indicators, don’t know how well it works for wing posts, I don’t use those ties
What I like to do with all these poly’s is take a look at their physical properties.The important one to me is the specific gravity. Less than 1 is going to float a fly real good, the greater away from 1 the better for nymphs and streamers.
Dunk some samples in a bowl of water and you will find that the physical properties show themselves right away, the heavier stuff sinks and the lighter stuff floats real good. You can find all you need to know about synthetic fibers by searching wikipedia using common or scientific names of the material you are looking at.
FYI, polypropylene’s (Fly-Rite) selling point when introduced in the 70’s was a specific gravity lighter than water.
These are some rules I follow when using synthetics. It was harder before internet to get this info, but it’s all on the keyboard now. Have a good time searching.
I’ll second the vote for Widow’s Web. I is easy to work with, comes in a variety of colors and it floats very well - it doesn’t hold as much water between the fibers as some of the other synthetics.