Fig 1The 15° rule, measuredHover to scrub · space to playrelease · 160° → 170° · extension 10°
Stance's tracked points; the angle is shoulder–elbow–wristIndex line on the moving arm: the elbow angle nowDrag pointer, latched as the upper arm passes horizontalThe 15° window engraved from it, toward straightThe ICC's 15-degree rule measures change, not bend: how far the elbow straightens between the moment the upper arm reaches horizontal in the upswing and the moment the ball is released. Here a goniometer on the arm shows it. The drag pointer latches when the bubble vial centres (upper arm horizontal), the window engraved from it is 15° wide, and the index line has to stay inside it until release. Legal: 160° at horizontal, 170° at release, 10° of extension, the guide's example. Illegal: 150° at horizontal, bending further to 146° in the first half of the window, then 168° at release: 22° of straightening from the most-bent point, which is how the extension is counted, and more than 15. Bent arm: flexed 20° (160°) at horizontal and still 160° at release, so 0° of extension: legal however bent it looks. All three arms are illustrative; every angle is read back from the skeleton's own shoulder, elbow and wrist. The window lasts 0.08 s here (the guide's "roughly a tenth of a second"), played 24× slower. Hyperextension past straight is discounted by the rule; none of these arms reaches it. Stance estimates this angle from ordinary phone video, as information, not an official ruling.
Stance Cricket™Stance Lab · Bowling law