All Mepps Aglia Longs are deep running spinners with willow leaf blades. The blade "hugs" the body of the spinner during retrieve, allowing it to stay in deep pockets long enough to attract a wide variety of fish.
Lure size is important. The rule of thumb is use smaller lures to catch smaller fish and larger lures to catch larger fish. Keep in mind plain spinners present a smaller profile than dressed spinners, so they will appear smaller to the fish. This makes them perfect for panfish and small stream trout. Fishing with dressed spinners can produce larger fish, but, when stream trout fishing, you will probably catch more fish using plain spinners.