The Hank Haney Strike Zone maintains its shape after you hit it, perserving a "snapshot" or your swing at impact. You can then analyze your body and club positions and adjust your swing accordingly. Simply fill the bag with towels, shirts or other cloth and practice striking the bag at 50% effort concentrating on your form. The bag is durable enough to strike with full force, but we recommend using 75% to 80% effort as you would when swinging on the course.