Semperfli Nano Silk Ultra 30D 18/0

To be honest I was reluctant to tie any smaller (<18) flies before discovering the Semperfly Nano Silk. I am now using the 30D for not only the very small flies (dries and nymphs too). It is very convenient to tie pretty much everything 14 and up; I think there is no competitor for this thread on deer hair flies, you can fairly call it unbreakable. While not the cheapest I found that allowing myself the comfort of using good quality materials it is totally worth it - just think about it, how many flies you tie with one bobbin of thread … 
Dakota Angler always met all my expectations and are one of my favorite sources for fly fishing gear and fly tying material - good inventory, they ship quick, and have good prices.