When it comes to tying flies, monofilament thread is either a blessing or a curse. It’s available in different diameters – here, 4/1000’s and 6/1000’s.
For comparison, 6x tippet material is usually 5/1000’s of an inch in diameter. It’s important to note that monofilament tying thread, although similar, has different properties than tippet material that make it more suitable for tying.
Mono thread is quite strong – which is certainly a big pro. Saltwater guys who often tie on large hooks, love the stuff because of its strength, its little bit of stretch and the fact that even multiple layers of it allow a color beneath to show through. This is especially true when a top coat of resin is applied. Mono thread is really a must for patterns like Bob Popovic’s Surf Candy.
One of its major downsides is the fact that mono thread is slippery, because it’s smooth and round. This is a serious con, even a deal-killer for many tiers. This slipperiness however actually becomes an advantage when spinning deer hair as on a Bomber or the head of a Muddler Minnow because everything just wants to spin smoothly around the hook shank.