Brandon,
I have used YLI silk for several years. Many different colors. Comes in either 200 meter spools that fit in most standard size bobbins. Also comes in 1000 meter cones. This thread is 100% filament silk, 2 ply, tex 12, 124 denier.
http://www.roserushbrooke.com/yli-silk-thread-1.html
These folks have always given me excellent service and are fly tying / rod making smart. I tie all of my flies with it as it is almost the same dia of 8/0 thread. I also use it for all of my rod wrapping.
I hope this helps you.
Denny