J:Son Sweden's Mayfly Dun is an imitation of adult mayfly. It has an extension body and realistic wings.

Adult mayfly imitations are choice for grayling, char and rainbow & brown trout. Mayflies are found world wide and that's why mayfly imitations are popular in every fisherman's fly box. With adult mayfly imitations fishing is best in early summer, May and June.

In the chart below you can see approximate fly and hook sizes: