Hemingway's Gammarus Back- These Gammarus backs are made from a unique material which is perfect for tying realistic Gammarus (shrimp) patterns. They are pre-cut, pre-formed, flexible, waterproof, and UV resistant. Just tie one in, create an underbody, and rib through with mono or wire. Top with Deer Creek Diamond Flex UV Resin- Flexible for an even more realistic look. 36 per pack. 3 sizes (12 per size).