The Iso is, on many rivers, the last big (in size) mayfly of the season. It’s well imitated by a parachute pattern. Watch the live tie-off and vote in real time if Tim or Tom ties the best version.
Iso Parachute Dry Fly
Hook: Standard or 2XL dry fly hook, size 12
Thread: White 8/0 (70 Denier).
Tail: Moose body hair.
Post: White polypropylene floating yarn, Fulling Mill Ultra Dry Yarn, or EP Trigger Point fibers (For ultra realism but less visibility can also use dark dun yarn)
Body: Isonychia or dark reddish brown dry fly dubbing (mix Rusty Spinner color with black or dark brown).
Hackle: dark dun hackle.