These are super quality 1 gram packs of CDC feathers from Chevron Hackles.  These have been dyed sympathetically in a range of attractive colours.
 
There are a range of simple to tie dry patterns that rely on the buoyant qualities of CDC feathers to hold your fly in the surface tension.  A favourite is the Shuttlecock pattern – with a simple thread or stripped quill body; the thorax is formed by folding a bunch of CDC  feathers over and trimmed over the eye.