Since the late 1960s (when Gordon Clark found the optimum formulation of urethane foam), many of the surfboards in common use have been of the shortboard variety between six and eight feet in length, with a pointed nose and a rounded or squarish tail, typically with three skegs (fins) but sometimes with one or two or as many as six. Surfers generally find a shortboard very quick to maneuver compared with other types of surfboards, but because of a lack of flotation due to the smaller size, harder to catch waves with, often requiring steeper, larger and more powerful waves and very late takeoffs, where the surfer catches the wave at the critical moment before it breaks.