Bulge and Roll is designed with progressively more curvature toward the heel/toe and high/low. By rounding the contours of the clubface, Bulge & Roll manipulates the launch and spin of off-center strikes, producing improved accuracy and more consistent distance.
Without Bulge and Roll, a flat metalwood clubface would greatly suffer from Gear Effect, leading to a substantial dip in performance. Instead, Bulge & Roll counteracts the tendencies of Gear Effect by precisely shaping the clubface in a way that delivers greater consistency in performance on off-center shots.
Based on the point of impact, the benefits of Bulge & Roll are experienced in two key ways: distance and accuracy.
DISTANCE
Without Bulge and Roll: On a low-face strike, a perfectly flat face would produce low launch and high spin, resulting in less overall distance.
With Bulge and Roll: The “roll” contour decreases loft, which imparts more speed and less spin onto the ball which produces overall distance that’s more consistent with a center-face impact.
ACCURACY
Without Bulge and Roll: On a toe strike on a perfectly flat face would produce a shot that starts fairly straight with increased sidespin, causing the ball to hook off target.
With Bulge and Roll: The “bulge” contour reduces sidespin and intentionally starts the ball further toward the right (for right-handed golfers) to let the remaining sidespin bring the ball back left toward the intended target.