The HMG Gammarus back are precut for giving your fly a realistic and easy to tie look. Use a curved hook, add some weight, some dubbing and a rib and you are ready to tie a perfect gammarus or shrimp imitation in no time a true killer for both freshwater and saltwater fly fishing. Gammarus nymphs are deadly for trout & grayling and indeed for coastal fishing for sea trout or sea run browns, so a gammarus pattern is a must-have-in-the-box pattern when fishing.