The Ace Hi-Fly features a double glow head that intensifies the action. The four facets on the head increase the erratic action of the fly when fished behind a dodger or a flasher. The way the insert puffs out the Mylar and plastic legs it gives the lure a pulsing action in the water. The Mylar itself reflects UV light. Salmon can see 3 more colors than humans; these all falling in the UV light spectrum. So with the special tinsel in the fly it literally lights up in the water. When bringing a fish to the boat you see the fly long before you see the fish.