The Sea Striker Planer is a sophisticated and precisely-balanced piece of fishing gear. The lead acts as a keep and balance weight to keep the planer running true at controlled depths. When the planer is in the water in diving position, water pressure against the blade forces the planer down. When a fish strikes, the balance is changed. The planer then trips and produces a slight upward drag. This allows you to fight your fish, rather than deal with a heavy lead sinker.