This is a imitation of a large caddisfly like for example "grandis". They exist in most parts of Europe and is very dominant i Scandinavia during June-August. They vary in colour and size so check you local preferences.
Please note the number at the end of the fly name is related to the size of fly and not the amount you will receive.
So for example Mayfly Nymph 3 is only one fly and not x3.