This pattern came from Grabflies "King Intruder Leech, Red". I have caught a lot of Steelhead on this pattern. Also see Custom Blue Flash Moal Leech, and Coho Salmon.
Fly is tied using black cross cut rabbit strip tied on braid line like a Moal Leech, then lots of Blue Rhea spun on, followed by Blue Flashabou, and Blue Guinea and red bead cone. The Black Rabbit core gives this fly lots of silhouette and animates the flashabou.