and provides users with a similar experience to combustibles. However, there remains a heated tobacco category's penetration going forward. After testing a range of variables (including price, menthol share, attempts to quit, personality scores) across over 40 markets and statistical methods, we used spline regressions with the independent variables of smoking prevalence, tar levels, and vapour penetration. NB Spline for each segment), rather than a single continuous curve, which is particularly helpful in factors (eg covid) and adjustments in the independent variables. The regression (R^2 of 0.82) provides a template path for heated tobacco penetration that countries tend to