A must-have in any fly-tyers kit. White River Fly Shops Flash-A-Bou Tying Material consists of flat mylar strands with maximum light-reactive surface area and tremendous movement a proven combination that entices lethargic fish to strike. Great for adding attention-getting flash to streamer wings, ribbing on midges, or wing cases on nymphs and other flies without putting on weight. 10 hank. Color: Ice Blue Pearl. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Tying Material.