Silicone "Grizzly Leggs"
Silicone Leggs are a critical now days on many patterns. They add lots of lifelike wiggle. They work well tied in X style on dry fly patterns like adult stones and tied on the side on your nymph thorax's. Spirit River also make their own Round Rubber Legs now that have been hand barred. They call them Tarantula legs.
Either one will give many of your flies a distinct advantage.
Caution...do not store rubber in direct light. Like a rubber band...they will eventually rot.