Sometimes we can't get the flies we fish from the big fly tying companies. In some cases the flies available from suppliers are overdressed. That makes sense since they look better in the bin and "more" worthy of purchase. At other times the materials might not be available in quantities sufficient to supply the market. Or it's the right fly on a mediocre hook.
Therefore we have a series of "Guide Flies" that are tied to our specs by local guides. Tied the way we like them and the way we fish them.