AMO (Archery Manufacturers and merchants Organization) standard draw length is the distance from the string at full draw to the lowest point on the grip plus . Because the draw force may increase more or less rapidly, and again drop off more or less rapidly when approaching peak draw, bows of the same peak draw force can store different amounts of energy. Norbert Mullaney has defined the ratio of stored energy to peak draw force (S.E./P.D.F.). This is usually around but can reach .