The global dun is an imitation of small and medium mayfies that, after emerging, ride the surface before becoming airborne. If the devil is in the details this fly is definetly not a saint.
Up north there is an island where pike leave is the mighty salt water of the Batlic sea
The Große (big) Lauter is a chalkstream in Germany that has good hatches of the real Mayfly (E.danica) between end May and mid June
The Asp is most of the time an elusive ghost. But when the day comes, it is a day you will remember for a long time.
The six-piece 8-foot is in the rucksack along with a box of flies, a reel and the vest. The rod must fit in the rucksack, you must avoid external tube holders that can get stuck in difficult passages.
  If the Mediterranean sea can offer good game fish, it ain't easy to catch them. I ventured out with the boat and had a great day fly-fishing with poppers.
When Asp hunt close to the surface there is no other imitation that can compete with this fly.
They approach the coast once a year to mate and they are hungry. From the shore or with the belly boat, where to find them, what flies are the best, find it in this video
This fly is fantastic for slow flowing streams, when the fish feed on rising nymphs and disregard anything else. It can be tied in different colors, the recommended ones being olive/tan, light olive/dark olive, gray/black