"Release ratio" denotes the ratio of the ball's forward (translational) speed to its rev rate (rotational speed) at time of release. This ratio continually decreases throughout the ball's travel until it reaches exactly 1.0 when full traction is achieved upon entering the roll phase. A too-"high" release ratio (a "speed-dominant" release) causes the ball to reach the pins while still in the hook phase (resulting in a shallow angle of entry that permits ball deflection and resultant leaves of the 10-pin), and a too-"low" release ratio (a "rev-dominant" release) causes the ball to enter the roll phase before reaching the pins (sacrificing power to friction that would ideally be delivered to the pins to enhance pin scatter). Ball speed and rev rate are said to be "matched" if the ball enters the roll phase immediately before impacting the pins, maximizing power imparted to the pins yet helping to provide an entry angle that minimizes ball deflection.• (date is approximate)</ref>