The Eyeline Golf Slow Mo screen will identify how your ball is reacting during the putting stroke. A ball with backspin, topspin, hopping & skidding all affect distance & accuracy, use the Slow Mo screen with the Myroll ball (supplied) & your own smartphone with Slo-mo video. Watch with amazement how good your putt rolls, or not! & make the relevant adjustments via shaft lean, tempo or ball position.