The freestyle kick butterfly drill is a great way to work on the 'head throw' in Butterfly. Most swimmers don't emphasize this critical technique in Butterfly (and Breaststroke) resulting in not only a slower stroke rate but a less powerful pull and kick. Using a freestyle kick during butterfly allows the swimmer to feel the 'surge' one gets from 'throwing the head down' as hard as a Martial Artist breaks a board with their head. Timing this head throw will ultimately lead to more efficient and faster swim.