When you need one fly, pick one that works..
In simpler times my fly box held a fraction of the patterns now found there on any given outing. Having more than a few years to accumulate my current collection has something to do with it, but mostly the difference was back in the "old days" I carried only what worked for me.
While the concept of "match the hatch" wasn't foreign, I didn't buy into the idea that fish could tell the difference between a BWO and a tan Caddis in the frothing waters of the Deschutes near White Horse. My inexperience didn't give my quarry that much intelligence nor the power to reason. Evidently, as I have gained experience those same fish have become smarter and I have not.
As a purveyor of fine fly tackle for over 20 years it is not in my best interest to minimize the requirements for an enjoyable day on the water, but on this occasion, I will emphasize that if one were to head off on a Trout fishing adventure with only one pattern in their box the Adams would be at the top of my list- Moose tail or not.
The Adams has the one defining characteristic that makes it a "must-have" pattern: it simply looks like food. Trout food to be exact! An assortment of different sizes is all that is required to crack the code on any given Trout stream on any given day. If an Adams doesn't get it done, there is always beer.
Hook: TMC 900 BL or your favorite dry fly hook
Thread: Black UTC 70
Tail: Moose hair
Body: Gray Dubbing
Wings: Grizzly hackle tips