When you’re fishing small flies – sizes 16 and smaller – you want to make sure that your don’t give a big trout too many opportunities to use the heavy current, and you want to do whatever it takes to play the fish as quickly as possible.

Also look at:
http://flyfishing-blog.com/flyfishing-blog.com/2019/06/10/new-orvis-tactical-nymph-leader/
http://flyfishing-blog.com/flyfishing-blog.com/2019/06/05/orvis-clearwater-nymph-set/
http://flyfishing-blog.com/flyfishing-blog.com/2019/04/29/german-orvis-fly-fishing-catalogue-published/