Description
The Slate Grey Dun #12: The Shadow on the Surface
The stage of the newly hatched adult Mayfly, known as the Dun, is the most critical phase for any fly angler. During this transition, the insect is at its most vulnerable, struggling to dry its wings before taking flight. On overcast days or during cooler hatches, the Slate Grey coloration is a dominant and vital profile for trout and grayling.
J:son Mayfly Dun – Slate Grey The Specialist for Dark Hatches & Overcast Days
The J:son Mayfly Dun in Slate Grey is a technical masterpiece designed to imitate the "skiffergrå" (slate grey) duns that dominate river systems and lakes, such as the large Siphlonurus (Large Brook Dun) and various Leptophlebia species. Its matte, dark-toned silhouette is specifically developed for those moments when fish become notoriously selective due to specific light conditions or concentrated hatches of darker insects.
Why this fly delivers:
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Scientific Anatomy: The extended foam body and precisely shaped upright wings create the iconic "sail" silhouette. This specific footprint on the water film is the primary strike trigger for trophy fish.
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Slate Grey Optics: The matte, non-reflective slate grey wing material mimics the natural opacity of a newly hatched dun’s wings, passing the "inspection test" even in crystal-clear water.
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Unsinkable Foam Technology: Utilizing J:son’s proprietary foam-body technology, this fly offers incredible buoyancy. It rides high and stable, ensuring it remains visible and effective even in turbulent or broken water.
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Realistic Light Refraction: The air-trapping wing surface reflects light exactly like a natural insect, creating a lifelike aura that triggers aggressive takes.
Pro Tip: Due to the realistic surface area of the wings, we highly recommend using a J:son Swivel. This prevents line twist during casting and ensures a perfect, natural presentation every time.