8/0 - Suitable for standard to small size tying For dry and nymph flies
6/0 - Stronger than 8/0, yet only a bit larger diameter. You can spin small(muddler) deer-hair & streamers with this
3/0 - Used to tie saltwater & bass flies. It's fine diameter and strong. Wraps flat. Strong enough to spin deer-hair, or tie wool-head sculp
