Stimulators are a reliable fly throughout the West for stonefly hatches. They look realistic, float well and work under a variety of conditions. Their hair wing adds just the right profile to fool cautious trout and their palmered hackle adds extra realism. Per 12. Sizes: 10, 12, 14. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Fly Assortments.