The primaries are usually the largest feathers on the wing. A pair of mallard wings will tie a huge range of standard patterns. You can tie larger fly's than 12 using duck quills. If you find you enjoy tying them and want to try colored married wings, Nature's Spirit brand has pretty good quality quills. Order at least double what you'll think you need. You go through quite a few, since not all the wings will set picture perfect every time, at least not for me anyway. Other brands tend to have many beat up, ragged pairs that you just can't use as much of the feather.