Red Tag - one of the most universal flies for trout, grayling and chub.
Red Tag looks like this: a small bloody red tag, a body from a peacock herl, a hackle of rusty cock feather from the rooster's throat. I always carry Red Tag in three sizes (No. 12, 16, 18) in three pieces of each size.
Nowadays there are dozens of variants of red tag - either dry flies, wet flies, nymphs, jigs...
Some other variants of Red Tag: