Do not underestimate this fly, the Brassie is one of the best small nymph patterns that there is. We use this on a variety of streams especially during the fringe months in the spring and fall. It imitates a chironomid or midge pupae this lives underwater and is levitating mid water column. Use this fly under a strike indicator or dry fly on streams, but don't overlook using it in lakes under a small strike indicator as well.
The Brassie is likely the most under-utilized "Big Trout" patterns there is. It looks like a variety of things and the shiny body and bead reflect surrounding light when underneath and this fly will take on the natural segmented look of a real insect. It is a Midge Larvae at heart but you will find that it fishes year round almost everywhere. Our guides love it because of its density and fish it underneath a dry fly very often.